生物工程专业英语

生物工程专业英语 Specialized English in Biotechnology This material is dedicated to students majoring in Biotechnology at Hefei University. All rights reserved Contents Lesson 1 What is Biotechnology? .............................................................................................................. 2 Lesson 2 Where Did Biotechnology Begin? .............................................................................................. 3 Lesson 3 Brief History of Biotechnology .................................................................................................. 5 Lesson 4 Dogma, DNA, and Enzymes....................................................................................................... 7 Lesson 5 Polymerase Chain Reaction - Xeroxing DNA ............................................................................ 9 Lesson 6 Monoclonal Antibody Technology ........................................................................................... 11 Lesson 7 The Human Genome Project..................................................................................................... 13 Lesson 8 Whose Genome is It, Anyway? ................................................................................................. 16 Lesson 9 Agriculture - An Overview ....................................................................................................... 18 Lesson 10 Gene Gun Speeds Search for New Orchid Colors .................................................................. 21 Lesson 11 Transforming Plants ................................................................................................................ 23 Lesson 12 Animals and Animal Health .................................................................................................... 26 Lesson 13 Biomining ............................................................................................................................... 28 Lesson 14 Biofuel .................................................................................................................................... 29 Lesson 15 New Foods and Food Producers ............................................................................................. 31 Lesson 16 Blazing a Genetic Trail in Medicine ....................................................................................... 34 Reading materials..................................................................................................................................... 36 1 Lesson 1 What is Biotechnology? Biotechnology in one form or another has flourished since prehistoric times. When the first human beings realized that they could plant their own crops and breed their own animals, they learned to use biotechnology. The discovery that fruit juices fermented into wine, or that milk could be converted into cheese or yogurt, or that beer could be made by fermenting solutions of malt and hops began the study of biotechnology. When the first bakers found that they could make a soft, spongy bread rather than a firm, thin cracker, they were acting as fledgling biotechnologists. The first animal breeders, realizing that different physical traits could be either magnified or lost by mating appropriate pairs of animals, engaged in the manipulations of biotechnology. What then is biotechnology? The term brings to mind many different things. Some think of developing new types of animals. Others dream of almost unlimited sources of human therapeutic drugs. Still others envision the possibility of growing crops that are more nutritious and naturally pest-resistant to feed a rapidly growing world population. This question elicits almost as many first-thought responses as there are people to whom the question can be posed. In its purest form, the term "biotechnology" refers to the use of living organisms or their products to modify human health and the human environment. Prehistoric biotechnologists did this as they used yeast cells to raise bread dough and to ferment alcoholic beverages, and bacterial cells to make cheeses and yogurts and as they bred their strong, productive animals to make even stronger and more productive offspring. Throughout human history, we have learned a great deal about the different organisms that our ancestors used so effectively. The marked increase in our understanding of these organisms and their cell products gains us the ability to control the many functions of various cells and organisms. Using the techniques of gene splicing and recombinant DNA technology, we can now actually combine the genetic elements of two or more living cells. Functioning lengths of DNA can be taken from one organism and placed into the cells of another organism. As a result, for example, we can cause bacterial cells to produce human molecules. Cows can produce more milk for the same amount of feed. And we can synthesize therapeutic molecules that have never before existed. 2 Lesson 2 Where Did Biotechnology Begin? With the Basics Certain practices that we would now classify as applications of biotechnology have been in use since man's earliest days. Nearly 10,000 years ago, our ancestors were producing wine, beer, and bread by using fermentation, a natural process in which the biological activity of one-celled organisms plays a critical role. In fermentation, microorganisms such as bacteria, yeasts, and molds are mixed with ingredients that provide them with food. As they digest this food, the organisms produce two critical by-products, carbon dioxide gas and alcohol. In beer making, yeast cells break down starch and sugar (present in cereal grains) to form alcohol; the froth, or head, of the beer results from the carbon dioxide gas that the cells produce. In simple terms, the living cells rearrange chemical elements to form new products that they need to live and reproduce. By happy coincidence, in the process of doing so, they help make a popular beverage. Bread baking is also dependent on the action of yeast cells. The bread dough contains nutrients that these cells digest for their own sustenance. The digestion process generates alcohol (which contributes to that wonderful aroma of baking bread) and carbon dioxide gas (which makes the dough rise and forms the honeycomb texture of the baked loaf). Discovery of the fermentation process allowed early peoples to produce foods by allowing live organisms to act on other ingredients. But our ancestors also found that, by manipulating the conditions under which the fermentation took place, they could improve both the quality and the yield of the ingredients themselves. Crop Improvement Although plant science is a relatively modern discipline, its fundamental techniques have been applied throughout human history. When early man went through the crucial transition from nomadic hunter to settled farmer, cultivated crops became vital for survival. These primitive farmers, although ignorant of the natural principles at work, found that they could increase the yield and improve the taste of crops by selecting seeds from particularly desirable plants. 3 Farmers long ago noted that they could improve each succeeding year's harvest by using seed from only the best plants of the current crop. Plants that, for example, gave the highest yield, stayed the healthiest during periods of drought or disease, or were easiest to harvest tended to produce future generations with these same characteristics. Through several years of careful seed selection, farmers could maintain and strengthen such desirable traits. The possibilities for improving plants expanded as a result of Gregor Mendel's investigations in the mid-1860s of hereditary traits in peas. Once the genetic basis of heredity was understood, the benefits of cross-breeding, or hybridization, became apparent: plants with different desirable traits could be used to cultivate a later generation that combined these characteristics. An understanding of the scientific principles behind fermentation and crop improvement practices has come only in the last hundred years. But the early, crude techniques, even without the benefit of sophisticated laboratories and automated equipment, were a true practice of biotechnology guiding natural processes to improve man's physical and economic well-being. Harnessing Microbes for Health Every student of chemistry knows the shape of a Buchner funnel, but they may be unaware that the distinguished German scientist it was named after made the vital discovery (in 1897) that enzymes extracted from yeast are effective in converting sugar into alcohol. Major outbreaks of disease in overcrowded industrial cities led eventually to the introduction, in the early years of the present century, of large-scale sewage purification systems based on microbial activity. By this time it had proved possible to generate certain key industrial chemicals (glycerol, acetone, and butanol) using bacteria. Another major beneficial legacy of early 20th century biotechnology was the discovery by Alexander Fleming (in 1928) of penicillin, an antibiotic derived from the mold Penicillium. Large-scale production of penicillin was achieved in the 1940s. However, the revolution in understanding the chemical basis of cell function that stemmed from the post-war emergence of molecular biology was still to come. It was this exciting phase of bioscience that led to the recent explosive development of biotechnology. 4 Lesson 3 Brief History of Biotechnology Biotechnology seems to be leading a sudden new biological revolution. It has brought us to the brink of a world of "engineered" products that are based in the natural world rather than on chemical and industrial processes. Biotechnology has been described as "Janus-faced." This implies that there are two sides. On one, techniques allow DNA to be manipulated to move genes from one organism to another. On the other, it involves relatively new technologies whose consequences are untested and should be met with caution. The term "biotechnology" was coined in 1919 by Karl Ereky, an Hungarian engineer. At that time, the term meant all the lines of work by which products are produced from raw materials with the aid of living organisms. Ereky envisioned a biochemical age similar to the stone and iron ages. A common misconception among teachers is the thought that biotechnology includes only DNA and genetic engineering. To keep students abreast of current knowledge, teachers sometimes have emphasized the techniques of DNA science as the "end-and-all" of biotechnology. This trend has also led to a misunderstanding in the general population. Biotechnology is NOT new. Man has been manipulating living things to solve problems and improve his way of life for millennia. Early agriculture concentrated on producing food. Plants and animals were selectively bred, and microorganisms were used to make food items such as beverages, cheese, and bread. The late eighteenth century and the beginning of the nineteenth century saw the advent of vaccinations, crop rotation involving leguminous crops, and animal drawn machinery. The end of the nineteenth century was a milestone of biology. Microorganisms were discovered, Mendel's work on genetics was accomplished, and institutes for investigating fermentation and other microbial processes were established by Koch, Pasteur, and Lister. Biotechnology at the beginning of the twentieth century began to bring industry and agriculture together. During World War I, fermentation processes were developed that produced acetone from starch and paint solvents for the rapidly growing automobile industry. Work in the 1930s was geared toward using surplus agricultural products to supply industry instead of imports or petrochemicals. The advent of World War II brought the manufacture of penicillin. The biotechnical focus moved to pharmaceuticals. 5 The "cold war" years were dominated by work with microorganisms in preparation for biological warfare, as well as antibiotics and fermentation processes. Biotechnology is currently being used in many areas including agriculture, bioremediation, food processing, and energy production. DNA fingerprinting is becoming a common practice in forensics. Similar techniques were used recently to identify the bones of the last Czar of Russia and several members of his family. Production of insulin and other medicines is accomplished through cloning of vectors that now carry the chosen gene. Immunoassays are used not only in medicine for drug level and pregnancy testing, but also by farmers to aid in detection of unsafe levels of pesticides, herbicides, and toxins on crops and in animal products. These assays also provide rapid field tests for industrial chemicals in ground water, sediment, and soil. In agriculture, genetic engineering is being used to produce plants that are resistant to insects, weeds, and plant diseases. A current agricultural controversy involves the tomato. A recent article in the New Yorker magazine compared the discovery of the edible tomato that came about by early biotechnology with the new "Flavr-Savr" tomato brought about through modern techniques. In the very near future, you will be given the opportunity to bite into the Flavr-Savr tomato, the first food created by the use of recombinant DNA technology ever to go on sale. What will you think as you raise the tomato to your mouth? Will you hesitate? This moment may be for you as it was for Robert Gibbon Johnson in 1820 on the steps of the courthouse in Salem, New Jersey. Prior to this moment, the tomato was widely believed to be poisonous. As a large crowd watched, Johnson consumed two tomatoes and changed forever the human-tomato relationship. Since that time, man has sought to produce the supermarket tomato with that "backyard flavor." Americans also want that tomato available year-round. New biotechnological techniques have permitted scientists to manipulate desired traits. Prior to the advancement of the methods of recombinant DNA, scientists were limited to the techniques of their time - cross-pollination, selective breeding, pesticides, and herbicides. Today's biotechnology has its "roots" in chemistry, physics, and biology . The explosion in techniques has resulted in three major branches of biotechnology: genetic engineering, diagnostic techniques, and cell/tissue techniques. 6 Lesson 4 Dogma, DNA, and Enzymes The Central Dogma Though it comes as no surprise that the composition of DNA between different organisms is different, it is not immediately obvious why the muscle cells, blood cells, and brain cells of any one particular vertebrate are so different in their structure and composition when the DNA of every one of their cells is identical. This is the key to one of the most exciting areas of modern cell biology. In different cell types, different sets of the total number of genes (genome) are expressed. In other words, different regions of the DNA are "active" in the muscle cells, blood cells, and brain cells. To understand how this difference in DNA activity can lead to differences in cell structure and composition, it is necessary to consider what is often known as the central dogma of molecular biology: "DNA makes RNA makes protein." In molecular terms, a gene is that portion of DNA that encodes for a single protein. The dictum "one gene makes one protein" has required some modification with the discovery that some proteins are composed of several different polypeptide chains, but the "one gene makes one polypeptide" rule does hold. DNA Contains the Blueprint for all Cell Proteins Messenger RNA is a precise copy (transcript) of the coded sequence of nucleic acid bases in DNA, and this message is translated into a unique protein molecule on specialist organelles (ribosomes) present in the cytoplasm of all cells. Proteins, which are largely made up of carbon (C), hydrogen (H), oxygen (0), and nitrogen (N), are constructed from 20 different, common amino acids. The versatility of proteins, the workhorse molecules of the cell, stems from the immense variety of molecular shapes that can be created by linking amino acids together in different sequences. The smaller proteins consist of only a few dozen amino acids, whereas the larger ones may contain in excess of 200 amino acids, all linked together in a linear chain by peptide bonds. As the proteins are released from the ribosome, they fold into unique shapes, under the influence of chemical forces that depend on the particular sequence of amino acids. So the protein primary sequence, encoded in the gene and faithfully transcribed and translated into an amino acid chain, determines the three-dimensional structure of the emerging molecule. The human body possesses some 30,000 different 7 kinds of proteins and several million copies of many of these. Each plays a specific role - for example, hemoglobin carries oxygen in the blood, actin and myosin interact to generate muscle movement, and acetylcholine receptor molecules mediate chemical transmission between nerve and muscle cells. Enzymes - Protein Biocatalysts An essential group of proteins - the enzymes - act as biological catalysts and regulate all aspects of cell metabolism. They enable breakdown of high-energy food molecules (carbohydrates) to provide energy for biological reactions, and they control the synthetic pathways that result in the generation of lipids (e.g., fats, cholesterol, and other vital membrane components), carbohydrates (sugars, starch, and cellulose - the key components of plant cell walls), and many vital small biomolecules essential for cell function. Though grouped together for their capacity to speed up chemical reactions that would proceed only very slowly at room temperature, different classes of enzymes vary greatly in their structure and function. Most cells contain about a thousand different enzymes, each capable of catalyzing a unique chemical reaction. 8 Lesson 5 Polymerase Chain Reaction - Xeroxing DNA Who would have thought a bacterium hanging out in a hot spring in Yellowstone National Park would spark a revolutionary new laboratory technique? The polymerase chain reaction, now widely used in research laboratories and doctor's offices, relies on the ability of DNA-copying enzymes to remain stable at high temperatures. No problem for Thermus aquaticus, the sultry bacterium from Yellowstone that now helps scientists produce millions of copies of a single DNA segment in a matter of hours. In nature, most organisms copy their DNA in the same way. The PCR mimics this process, only it does it in a test tube. When any cell divides, enzymes called polymerases make a copy of all the DNA in each chromosome. The first step in this process is to "unzip" the two DNA chains of the double helix. As the two strands separate, DNA polymerase makes a copy using each strand as a template. The four nucleotide bases, the building blocks of every piece of DNA, are represented by the letters A, C, G, and T, which stand for their chemical names: adenine, cytosine, guanine, and thymine. The A on one strand always pairs with the T on the other, whereas C always pairs with G. The two strands are said to be complementary to each other. To copy DNA, polymerase requires two other components: a supply of the four nucleotide bases and something called a primer. DNA polymerases, whether from humans, bacteria, or viruses, cannot copy a chain of DNA without a short sequence of nucleotides to "prime" the process, or get it started. So the cell has another enzyme called a primase that actually makes the first few nucleotides of the copy. This stretch of DNA is called a primer. Once the primer is made, the polymerase can take over making the rest of the new chain. A PCR vial contains all the necessary components for DNA duplication: a piece of DNA, large quantities of the four nucleotides, large quantities of the primer sequence, and DNA polymerase. The polymerase is the Taq polymerase, named for Thermus aquaticus, from which it was isolated. The three parts of the polymerase chain reaction are carried out in the same vial, but at different temperatures. The first part of the process separates the two DNA chains in the double helix. This is done simply by heating the vial to 90-95 degrees centigrade (about 165 degrees Fahrenheit) for 30 seconds. 9 But the primers cannot bind to the DNA strands at such a high temperature, so the vial is cooled to 55 degrees C (about 100 degrees F). At this temperature, the primers bind or "anneal" to the ends of the DNA strands. This takes about 20 seconds. The final step of the reaction is to make a complete copy of the templates. Since the Taq polymerase works best at around 75 degrees C (the temperature of the hot springs where the bacterium was discovered), the temperature of the vial is raised. The Taq polymerase begins adding nucleotides to the primer and eventually makes a complementary copy of the template. If the template contains an A nucleotide, the enzyme adds on a T nucleotide to the primer. If the template contains a G, it adds a C to the new chain, and so on to the end of the DNA strand. This completes one PCR cycle. The three steps in the polymerase chain reaction - the separation of the strands, annealing the primer to the template, and the synthesis of new strands - take less than two minutes. Each is carried out in the same vial. At the end of a cycle, each piece of DNA in the vial has been duplicated. But the cycle can be repeated 30 or more times. Each newly synthesized DNA piece can act as a new template, so after 30 cycles, 1 billion copies of a single piece of DNA can be produced! Taking into account the time it takes to change the temperature of the reaction vial, 1 million copies can be ready in about three hours. PCR is valuable to researchers because it allows them to multiply unique regions of DNA so that they can be detected in large genomes. Researchers in the Human Genome Project are using PCR to look for markers in cloned DNA segments and to order DNA fragments in libraries. 10 Lesson 6 Monoclonal Antibody Technology Substances foreign to the body, such as disease-causing bacteria, viruses and other infectious agents, known as antigens, are recognized by the body's immune system as invaders. Our natural defenses against these infectious agents are antibodies, proteins that seek out the antigens and help destroy them. Antibodies have two very useful characteristics. First, they are extremely specific; that is, each antibody binds to and attacks one particular antigen. Second, some antibodies, once activated by the occurrence of a disease, continue to confer resistance against that disease; classic examples are the antibodies to the childhood diseases chickenpox and measles. The second characteristic of antibodies makes it possible to develop vaccines. A vaccine is a preparation of killed or weakened bacteria or viruses that, when introduced into the body, stimulates the production of antibodies against the antigens it contains. It is the first trait of antibodies, their specificity, that makes monoclonal antibody technology so valuable. Not only can antibodies be used therapeutically, to protect against disease; they can also help to diagnose a wide variety of illnesses, and can detect the presence of drugs, viral and bacterial products, and other unusual or abnormal substances in the blood. Given such a diversity of uses for these disease-fighting substances, their production in pure quantities has long been the focus of scientific investigation. The conventional method was to inject a laboratory animal with an antigen and then, after antibodies had been formed, collect those antibodies from the blood serum (antibody-containing blood serum is called antiserum). There are two problems with this method: It yields antiserum that contains undesired substances, and it provides a very small amount of usable antibody. Monoclonal antibody technology allows us to produce large amounts of pure antibodies in the following way: We can obtain cells that produce antibodies naturally; we also have available a class of cells that can grow continually in cell culture. If we form a hybrid that combines the characteristic of "immortality" with the ability to produce the desired substance, we would have, in effect, a factory to produce antibodies that worked around the clock. 11 In monoclonal antibody technology, tumor cells that can replicate endlessly are fused with mammalian cells that produce an antibody. The result of this cell fusion is a "hybridoma," which will continually produce antibodies. These antibodies are called monoclonal because they come from only one type of cell, the hybridoma cell; antibodies produced by conventional methods, on the other hand, are derived from preparations containing many kinds of cells, and hence are called polyclonal. An example of how monoclonal antibodies are derived is described below. A myeloma is a tumor of the bone marrow that can be adapted to grow permanently in cell culture. When myeloma cells were fused with antibody-producing mammalian spleen cells, it was found that the resulting hybrid cells, or hybridomas, produced large amounts of monoclonal antibody. This product of cell fusion combined the desired qualities of the two different types of cells: the ability to grow continually, and the ability to produce large amounts of pure antibody. Because selected hybrid cells produce only one specific antibody, they are more pure than the polyclonal antibodies produced by conventional techniques. They are potentially more effective than conventional drugs in fighting disease, since drugs attack not only the foreign substance but the body's own cells as well, sometimes producing undesirable side effects such as nausea and allergic reactions. Monoclonal antibodies attack the target molecule and only the target molecule, with no or greatly diminished side effects. 12 Lesson 7 The Human Genome Project Since the beginning of time, people have yearned to explore the unknown, chart where they have been, and contemplate what they have found. The maps we make of these treks enable the next explorers to push ever farther the boundaries of our knowledge - about the earth, the sea, the sky, and indeed, ourselves. On a new quest to chart the innermost reaches of the human cell, scientists have now set out on biology's most important mapping expedition: the Human Genome Project. Its mission is to identify the full set of genetic instructions contained inside our cells and to read the complete text written in the language of the hereditary chemical DNA (deoxyribonucleic acid). As part of this international project, biologists, chemists, engineers, computer scientists, mathematicians, and other scientists will work together to plot out several types of biological maps that will enable researchers to find their way through the labyrinth of molecules that define the physical traits of a human being. Packed tightly into nearly every one of the several trillion body cells is a complete copy of the human "genome" - all the genes that make up the master blueprint for building a man or woman. One hundred thousand or so genes sequestered inside the nucleus of each cell are parceled among the 46 sausage-shaped genetic structures known as chromosomes. New maps developed through the Human Genome Project will enable researchers to pinpoint specific genes on our chromosomes. The most detailed map will allow scientists to decipher the genetic instructions encoded in the estimated 3 billion base pairs of nucleotide bases that make up human DNA. Analysis of this information, likely to continue throughout much of the 21st century, will revolutionize our understanding of how genes control the functions of the human body. This knowledge will provide new strategies to diagnose, treat, and possibly prevent human diseases. It will help explain the mysteries of embryonic development and give us important insights into our evolutionary past. The development of gene-splicing techniques over the past 20 years has given scientists remarkable opportunities to understand the molecular basis of how a cell functions, not only in disease, but in everyday activities as well. Using these techniques, scientists have mapped out the genetic molecules, or genes, that control many life processes in common microorganisms. Continued improvement of these biotechniques has allowed researchers to begin to develop maps of human chromosomes, which contain 13 many more times the amount of genetic information than those of microorganisms. Though still somewhat crude, these maps have led to the discovery of some important genes. By the mid-1980s, rapid advances in chromosome mapping and other DNA techniques led many scientists to consider mapping all 46 chromosomes in the very large human genome. Detailed, standardized maps of all human chromosomes and knowledge about the nucleotide sequence of human DNA will enable scientists to find and study the genes involved in human diseases much more efficiently and rapidly than has ever been possible. This new effort - the Human Genome Project - is expected to take 15 years to complete and consists of two major components. The first - creating maps of the 23 pairs of chromosomes - should be completed in the first 5 to 10 years. The second component - sequencing the DNA contained in all the chromosomes - will probably require the full 15 years. Although DNA sequencing technology has advanced rapidly over the past few years, it is still too slow and costly to use for sequencing even the amount of DNA contained in a single human chromosome. So while some genome project scientists are developing chromosome maps, others will be working to improve the efficiency and lower the cost of sequencing technology. Large-scale sequencing of the human genome will not begin until those new machines have been invented. Why do the Human Genome Project? Most inherited diseases are rare, but taken together, the more than 3,000 disorders known to result from single altered genes rob millions of healthy and productive lives. Today, little can be done to treat, let alone cure, most of these diseases. But having a gene in hand allows scientists to study its structure and characterize the molecular alterations, or mutations, that result in disease. Progress in understanding the causes of cancer, for example, has taken a leap forward by the recent discovery of cancer genes. The goal of the Human Genome Project is to provide scientists with powerful new tools to help them clear the research hurdles that now keep them from understanding the molecular essence of other tragic and devastating illnesses, such as schizophrenia, alcoholism, Alzheimer's disease, and manic depression. Gene mutations probably play a role in many of today's most common diseases, such as heart disease, diabetes, immune system disorders, and birth defects. These diseases are believed to result from complex interactions between genes and environmental factors. When genes for diseases have been identified, scientists can study how specific environmental factors, such as food, drugs, or pollutants interact with those genes. 14 Once a gene is located on a chromosome and its DNA sequence worked out, scientists can then determine which protein the gene is responsible for making and find out what it does in the body. This is the first step in understanding the mechanism of a genetic disease and eventually conquering it. One day, it may be possible to treat genetic diseases by correcting errors in the gene itself, replacing its abnormal protein with a normal one, or by switching the faulty gene off. Finally, Human Genome Project research will help solve one of the greatest mysteries of life: How does one fertilized egg "know" to give rise to so many different specialized cells, such as those making up muscles, brain, heart, eyes, skin, blood, and so on? For a human being or any organism to develop normally, a specific gene or sets of genes must be switched on in the right place in the body at exactly the right moment in development. Information generated by the Human Genome Project will shed light on how this intimate dance of gene activity is choreographed into the wide variety of organs and tissues that make up a human being. 15 Lesson 8 Whose Genome is It, Anyway? A quick glance around any public gathering will attest to the physical diversity of the human population. In most groups of people, some will be tall, others hefty; some will have brown eyes, and others blue. Physical attributes such as height, complexion, and hair and eye color are largely determined by genes - packets of the genetic material DNA, which makes up chromosomes in the human cell. As scientists begin to map and analyze the molecular details of the complete set of human genes, whose will it be? In many ways, describing the anatomy of the human genome will be similar to studying the human heart, for example, or the human brain. While there are small differences from person to person in the size and shape of these organs, most of the key characteristics are the same. Although human beings are distinct from one another, they are really very similar in most biologically important respects. That's what makes us human. So the map of the human genome can really be based on information collected from many different people. And most of the information in that map will pertain to everyone. The tiny differences between any two people rest in only 2 to 10 million (out of the 3 billion total) nucleotide bases, an amount that computes to about 1 percent or less of their total DNA. Because these small differences vary from person to person, it doesn't matter whose genome it is. For some studies, the differences will be the focus of interest. In other cases, it will be the similarities. Researchers at Baylor College of Medicine were given the assignment of mapping the sex chromosome X and chromosome 17. They collected DNA from patients who came into the clinic for genetic testing. Each sample is from a different and unrelated person. The cell culture collection contains a number of different human genomes. Eventually, scientists will "map", or establish distinctive genetic landmarks, from one end of a chromosome to the other and add that information to the genetic map of the entire human genome. This complete map will become the "reference" to which researchers will compare DNA taken from a variety of people, as scientists look for disease genes and other important genetic regions located on chromosomes. A particular region on a chromosome, for example, may be found to contain information about height. Although the genetic content of that specific site may change slightly from person to person, the location of the site will be the same in each person's genome. 16 Because studying the entire six-foot stretch of human DNA is a huge project, scientists are tackling the genome one chromosome at a time. Even then, analyzing the information in just one chromosome is an enormous task for a single research group, so many scientists are studying only portions of a chromosome at a time. The complete map for a single chromosome will then be derived from samples collected from several unrelated people by researchers in many different laboratories. For several decades, geneticists searching for disease genes have studied human cells maintained in the laboratory. These cells originally came from people who have an inherited disease, from their healthy relatives who are carriers, or from other unrelated healthy people. But because human cells do not ordinarily survive long under laboratory conditions, scientists have had to invent ways to keep the cells alive long enough to perform detailed studies of DNA inside the cells. Since almost all cells in the body contain the same genetic information, nearly any type of cell can be used as a source of DNA. A type of white blood cell called a lymphocyte is commonly used because it is easy to obtain from a blood sample. To get the cells to last longer in the laboratory, scientists infect lymphocytes in the test tube with a common virus known as EBV. This virus, the cause of mononucleosis, interrupts the cell's normal life cycle so it literally doesn't know when to die. Cells "immortalized" by EBV then grow and divide indefinitely in laboratory cultures, providing researchers with unlimited amounts of human DNA for genome studies. In most labs, the donors of these pieces of biology's greatest puzzle will never be known. They are the genetic equivalent, according to one researcher, of the unknown soldier. 17 Lesson 9 Agriculture - An Overview Techniques aimed at crop improvement have been utilized for centuries. Today, applied plant science has three overall goals: increased crop yield, improved crop quality, and reduced production costs. Biotechnology is proving its value in meeting these goals. Progress has, however, been slower than with medical and other areas of research. Because plants are genetically and physiologically more complex than single-cell organisms such as bacteria and yeasts, The necessary technologies are developing more slowly. Improvements in Crop Yield and Quality In one active area of plant research, scientists are exploring ways to use genetic modification to confer desirable characteristics on food crops. Similarly, agronomists are looking for ways to harden plants against adverse environmental conditions such as soil salinity, drought, alkaline earth metals, and anaerobic (lacking air) soil conditions. Genetic engineering methods to improve fruit and vegetable crop characteristics - such as taste, texture, size, color, acidity or sweetness, and ripening process, are being explored as a potentially superior strategy to the traditional method of cross-breeding. Research in this area of agricultural biotechnology is complicated by the fact that many of a crop's traits are encoded not by one gene but by many genes working together. Therefore, one must first identify all of the genes that function as a set to express a particular property. This knowledge can then be applied to altering the germlines of commercially important food crops. For example, it will be possible to transfer the genes regulating nutrient content from one variety of tomatoes into a variety that naturally grows to a larger size. Similarly, by modifying the genes that control ripening, agronomists can provide supplies of seasonal fruits and vegetables for extended periods of time. Biotechnological methods for improving field crops, such as wheat, corn and soybeans, are also being sought, since seeds serve both as a source of nutrition for people and animals and as the material for producing the next plant generation. By increasing the quality and quantity of protein or varying the types in these crops, we can improve their nutritional value. For example, a major protein of corn has 18 very little of two amino acids, lysine and tryptophan, which are essential for human growth. Increased amounts of these amino acids could make corn products a source of improved protein. Biopesticides and Biofertilizers Biotechnology makes it possible to develop bacteria essential to herbicide and other pesticide compounds. Certain chemicals produced by these organisms are called allelopathic agents. These chemicals act as natural herbicides, preventing the growth of other plant species in the same geographic area. Black walnut trees, for example, release an allelopathic agent against tomato plants. Modern high-yield agriculture entails consumption of vast amounts of chemicals for use as fertilizers and as agents to control pests and plant diseases, and any means that will permit the plant to do this work itself could result in significant savings for the farmer. For example, soybeans and certain other legumes produce their own source of usable nitrogen fertilizer by a process known as nitrogen fixation. This process is made possible by a bacterium that grows symbiotically on the plant's roots. (In a symbiotic relationship, dissimilar organisms live together in a mutually beneficial way.) In the nitrogen-fixing process, microbes capture atmospheric nitrogen and biochemically convert it into water-soluble nitrogen. This form of nitrogen is an essential nutrient for increasing the quantity and quality of plant yield. This bacteria will not assist in the growth of other important crops, such as corn and cereal plants. But research on nitrogen-fixing bacteria and legumes may show how we can modify either the bacteria or non-leguminous plants, thereby making many crops more nearly self-sufficient in obtaining nitrogen. Biotechnology is central to the search for effective, environmentally safe and economically sound alternatives to chemical pesticides. Biotechnology may be used to protect commercial crop plants from insect pests and promises to guard against further environmental deterioration and to provide a useful alternative to traditional methods of insect pest control. Biopesticides degrade rapidly in the environment - a major environmental benefit. The active elements of bacterial pesticides are proteins that are fragile molecules. Once exposed to the sun and other natural elements, these proteins are quickly broken down, thereby prohibiting spread to groundwater and 19 other animal and plant species. This will help keep our water supply safe to drink, our lakes and streams habitable for water life and recreation. Unlike chemical pesticide technology, biopesticide technology is based on potent, naturally occurring proteins. These living particles are produced in nature by microorganisms such as Bacillus thuringiensis (B.t.). Discovered at the turn of the century, B.t. has been used without risk in the United States for almost three decades by home gardeners, farmers, and forestry officials. Its active component, a protein, specifically attacks the stomachs of target pests, disrupting their digestive tracks so thoroughly that the pests stop eating and eventually die of starvation. Higher organisms, such as mammals, fish, birds, and other non-target species remain unthreatened, however, because their stomach acid easily breaks down the protein toxin. The delivery of these biopesticides varies in method and design. In one method, dormant spores of B.t. are dusted on crops. The spores then become active and multiply, covering plants with a bacteria poisonous to the target insects that feed on them. The B.t. toxin gene can also be inserted into the genetic makeup of crops, giving them a built-in resistance to insects. Similarly, the toxin gene can be put into a third party, such as a microorganism that lives within the plant's sap. These organisms - known as endophytes - multiply within the host plant and move throughout the plant's vascular system, forming a microscopic defense against feeding insects. This process resembles vaccines moving throughout a person's vascular system to defend against harmful disease. Some of the concerns farmers raise about having to use increasingly dangerous pesticides to produce adequate crops may well be addressed by biotechnology. Further research in agricultural biotechnology and biopesticide development aims to provide attractive alternatives to the farmer that will lower overall unit cost of production and allow the farmer to be more competitive in the highly cost-sensitive world markets. While some uses of chemical pesticides will be necessary for decades to come, continued development by biotechnology companies of useful biological pesticides will offer farmers viable alternatives. 20 Lesson 10 Gene Gun Speeds Search for New Orchid Colors A corn gene is giving U.S. Department of Agriculture researchers a jump start in verifying what the color of a new flower will be. "If orchid plants are bred for a new color, it's anyone's guess about the outcome. Usually, the plant industry now waits three years until a bloom appears," said Robert J. Griesbach, a plant geneticist with USDA's Agricultural Research Service. "We found a corn gene that will give us results on the color of new hybrids in just three days," he said. That gene regulates the pigment in corn plants. Griesbach said the genetic technique - coating the corn DNA on microscopic gold pellets that are propelled, by a particle gun, into orchid flower petals - screens for genetic flaws in the parent plants crossed to breed new hybrids. "That should give plant breeders a higher degree of certainty in crossing various orchid colors like purple and yellow by cutting down on the number of unwanted color mutations," he said. About one in a thousand orchid plants lacks adequate pigments, causing white or near white flowers. Other mutations result in flowers that have varying degrees of purple pigment, ranging to about 25 percent of true purple color. "We have tested the technique successfully on bulb plants like gladiolas and other ornamentals like petunias, as well as on orchids," said Griesbach, an expert on flower pigmentation. "Genetic screening could result in a broader range of colors in orchids and other ornamental plants." Griesbach said the technique could be "a boon to breeders of orchids because of the flower's long generation time - up to six years in some commercial types." Orchid flowers are highly prized, he added, noting that potted phalaenopsis orchids are "fast becoming a major economic crop." Griesbach tried the faster genetic technique after removing white petals from orchid flowers (Doritis pulcherrima Lindl.). He bombarded the petals with microscopic (1-mm diameter) gold pellets coated with DNA taken from corn plants. 21 "Screening plants for color mutations is a new use for the particle gun that Bob Griesbach demonstrated for the first time," said Roger Lawson, National Arboretum, Washington, D.C. "The gold pellets were more than 10 times smaller than the dot at the end of this sentence," he said. Over more than two years of tests, Griesbach found that the introduced corn genes causes near-white flowers to gain pigment within 48 hours. On fully colored, wild-type flowers, the purple continued to develop for the next 24 hours. "Eventually, the orchid cells with the corn genes looked the same as the purple cells found in wild plants, without loss of pigment," Griesbach said. 22 Lesson 11 Transforming Plants Cloning of Plant Cells and Manipulation of Plant Genes Plant cells exhibit a variety of characteristics that distinguish them from animal cells. These characteristics include the presence of a large central vacuole and a cell wall, and the absence of centrioles, which play a role in mitosis, meiosis, and cell division. Along with these physical differences, another factor distinguishes plant cells from animal cells, which is of great significance to the scientist interested in biotechnology: Many varieties of full-grown adult plants can regenerate from single, modified plant cells called protoplasts - plant cells whose cell walls have been removed by enzymatic digestion. More specifically, when some species of plant cells are subjected to the removal of the cell wall by enzymatic treatment, they respond by synthesizing a new cell wall and eventually undergoing a series of cell divisions and developmental processes that result in the formation of a new adult plant. That adult plant can be said to have been cloned from a single cell of a parent plant. Plants that can be cloned with relative ease include carrots, tomatoes, potatoes, petunias, and cabbage, to name only a few. The capability to grow a whole plant from a single cell means that researchers can engage in the genetic manipulation of the cell, let the cell develop into a completely mature plant, and examine the whole spectrum of physical and growth effects of the genetic manipulation within a relatively short period of time. Such a process is far more straightforward than the parallel process in animal cells, which cannot be cloned into full-grown adults. Therefore, the results of any genetic manipulation are usually easier to examine in plants than in animals. A Cloning Vector that Works with Plant Cells Not all aspects of the genetic manipulation of plant cells are readily accomplished. Not only do plants usually have a great deal of chromosomal material and grow relatively slowly as compared with single cells grown in the laboratory, but few cloning vectors can successfully function in plant cells. While researchers working with animal cells can choose among a wide variety of cloning vectors to find just the right one, plant cell researchers are currently limited to just a few basic types of vectors. Perhaps the most commonly used plant cloning vector is the "Ti" plasmid, or tumor-inducing plasmid. This plasmid is found in cells of the bacterium known as Agrobacterium tumefaciens, which 23 normally lives in soil. The bacterium has the ability to infect plants and cause a crown gall, or tumorous lump, to form at the site of infection. The tumor-inducing capacity of this bacterium results from the presence of the Ti plasmid. The Ti plasmid itself, a large, circular, double-stranded DNA molecule, can replicate independently of the A. tumefaciens genome. When these bacteria infect a plant cell, a 30,000 base-pair segment of the Ti plasmid - called T DNA - separates from the plasmid and incorporates into the host cell genome. This aspect of Ti plasmid function has made it useful as a plant cloning vector. The Ti plasmid can be used to shuttle exogenous genes into host plant cells. This type of gene transfer requires two steps: 1) the endogenous, tumor-causing genes of the T DNA must be inactivated and, 2) foreign genes must be inserted into the same region of the Ti plasmid. The resulting recombinant plasmid, carrying up to approximately 40,000 base pairs of inserted DNA and including the appropriate plant regulatory sequences, can then be placed back into the A. tumefaciens cell. That cell can be introduced into plant cell protoplasts either by the process of infection or by direct insertion. Once in the protoplast, the foreign DNA, consisting of both T DNA and the inserted gene, incorporates into the host plant genome. The engineered protoplast - containing the recombinant T DNA - regenerates into a whole plant, each cell of which contains the inserted gene. Once a plant incorporates the T DNA with its inserted gene, it passes it on to future generations of the plant with a normal pattern of Mendelian inheritance. One of the earliest experiments that involved the transport of a foreign gene by the Ti plasmid involved the insertion of a gene isolated from a bean plant into a host tobacco plant. Although this experiment served no commercially useful purpose, it successfully established the ability of the Ti plasmid to carry genes into plant host cells, where they could be incorporated and expressed. A. Tumefaciens Infects a Limited Variety of Plant Types The fact that only certain types of plants were naturally susceptible to infection with the host bacterial organism initially limited the usefulness of the Ti plasmid as a cloning vector. In nature, A. tumefaciens infects only dicotyledons or "dicots" - plants with two embryonic leaves. Dicotyledenous plants, divided into approximately 170,000 different species, include such plants as roses, apples, soybeans, potatoes, pears, and tobacco. Unfortunately, many important crop plants, including corn, rice, and wheat, are monocotyledons - plants with only one embryonic leaf - and thus could not be easily transfected using this bacterium. 24 Overcoming the Limited Range of A. Tumefaciens Infection Research efforts in the past few years have reduced the limitations of A. tumefaciens. Scientists discovered that by using the processes of microinjection, electroporation, and particle bombardment, naked DNA molecules can be introduced into plant cell types that are not susceptible to A. tumefaciens transfection. Microinjection involves the direct injection of material into a host cell using a finely drawn micropipette needle. Electroporation uses brief pulses of high voltage electricity to induce the formation of transient pores in the membrane of the host cell. Such pores appear to act as passageways through which the naked DNA can enter the host cell. Particle bombardment actually shoots DNA-coated microscopic pellets through a plant cell wall. These developments, important in the commercial application of plant genetic engineering, render the valuable food crops of corn, rice, and wheat susceptible to a variety of manipulations by the techniques of recombinant DNA and biotechnology. 25 Lesson 12 Animals and Animal Health The National Animal Genome Research Program (NAGRP), recently approved as a USDA regional research project, has as a general goal the determination of the genetic makeup of various economically important domestic animals. Specific objectives of the program are (1) to improve our understanding of the structure and organization of specific genes, (2) to identify and characterize genes controlling important metabolic processes (such as growth, aspects of reproduction, and milk production), and (3) to assign these genes to specific locations on chromosomes, so that they can be more easily manipulated in breeding programs designed to enhance expression of specific traits. Integral to the process of genome mapping is the detection and characterization of "markers." Markers are sequences of DNA with unusual patterns or characteristics that are easily recognized, and the position of specific genes can be determined by ascertaining the location of the gene relative to a marker. Some have variable number tandem repeats; microsatellite markers are repeats of a simple DNA sequence (such as CACACACA, where C and A are the bases cytosine and adenine, respectively). Other markers may be identified on the basis of conformational differences. Responsibility for the various domestic species has been spread out over the geographic regions of the U.S., each supervised by an administrative advisor. The Animal Genome Technical Committee involves 51 scientists at 27 locations, and the industries for which these studies are relevant have been actively supportive of the program. Committees representing the major animal groups (swine, sheep, cattle, and poultry) are developing computer databases similar to that available for mice. These will serve as banks for genomic data representing the entire array of genes of a particular animal. The data will provide a basis for comparative studies among animals, to facilitate correlations between genes and their functions, and also to determine the relative positions of genes in the DNA sequence. The committee responsible for swine genome research has made significant progress in development of a genetic linkage map, with 400 markers already identified. The immediate goals for this committee include continuing to develop a genetic linkage map and to produce swine cells that can grow 26 independently in a laboratory setting to allow for constant availability. The swine database, USPIGBASE, is already available for use. Several genetic linkage maps for cattle have been produced, and these cover approximately 90% of the bovine genome. The U.S.-developed map contains 313 markers, and several hundred cattle microsatellite markers have been identified in the past year. The "international" map has 201 areas of genetic diversity and is the result of an international collaboration involving ten laboratories in seven countries. A major goal for the immediate future is to develop a consensus linkage map, combining information from all independent maps now available, and to subsequently develop a database from this information. The committee directing the mapping of the poultry genome is striving to develop a consensus genetic linkage map of chickens, with many easily identified markers, and to extend this map to other poultry of economic importance. Further, this map will be used to identify genes responsible for specific traits, to work with industries to develop effective applications for this knowledge, and to enhance progress in all of these areas through the sharing of information via a database. Recent efforts have seen the number of known markers increase to 230, and efforts to produce a consensus linkage map have begun, using several maps now available. Researchers in the sheep genome project have been successful in developing genetic linkage maps containing several hundred markers, and work on a consensus genetic linkage map is underway. Animal genetics and gene mapping have received major support through the National Research Initiative Competitive Grants Program (NRICGP) of the USDA. One primary objective of the NRICGP is to increase our understanding of the structure, organization, function, expression, and regulation of genes. Further knowledge in these areas will help to maintain genetic diversity, improve animal productivity and efficiency, locate economically important production traits (including size, reproductive vigor, and genetic diseases), and finally to provide methods for utilizing this information to select for desired characteristics in animals. 27 Lesson 13 Biomining Although mining is one of humankind's oldest activities, the techniques used to extract minerals haven't changed substantially for centuries. Ores are dug from the earth, crushed, then minerals such as copper and gold are extracted by extreme heat or toxic chemicals. The environmental and health effects of traditional mining technologies have been deleterious. In the past few years, the mining industry has been turning to a more efficient and environmentally salubrious method for extracting minerals from ores: microorganisms that leach them out. Using a bacterium such as Thiobacillus ferooxidans to leach copper from mine tailings has improved recovery rates and reduced operating costs. Moreover, it permits extraction from low grade ores - an important consideration in the face of the depletion of high grade ores. Thiobacillus ferooxidans, which is naturally present in certain sulfur-containing materials, gets energy by oxidizing inorganic materials, such as copper sulfide minerals. This process releases acid and an oxidizing solution of ferric ions, which can wash out metals from crude ore. Poor quality copper ore, which is bound up in a sulfide matrix, is dumped outside a mine and treated with sulfuric acid to encourage the growth of T. ferooxidans. As the bacteria chew up the ore, copper is released and collected in solution. The sulfuric acid is recycled. Currently 25% of all copper worldwide, worth more than $1 billion annually, is produced through bioprocessing. This ranks it as one of the most important applications of biotechnology today. Bioprocessing is also being used to economically extract gold from very low grade, sulfidic gold ores, once thought to be worthless. To increase the efficiency of biomining, the search is on for bacterial strains that are better suited to large-scale operations. Bioprocessing releases a great deal of heat, and this can slow down or kill the bacteria currently being used. Researchers are turning to heat-loving thermophilic bacteria found in hot springs and around oceanic vents to solve this problem. These bacteria thrive in temperatures up to 100 degrees Celsius or higher and could function in a high temperature oxidative environment. Another effort is underway to find - or genetically engineer - bacterial strains that can stand up to heavy metals such as mercury, cadmium, and arsenic, which poison microbes and slow the bioprocessing. Some microbes have enzymes that protect their basic activities from heavy metals or pump them out. If genes that protect microbes from heavy metals can be identified, resistant strains might be engineered. In any event, biomining is now at the top of mining technology, and future development of the technology appears promising. 28 Lesson 14 Biofuel According to the Volkswagen Corporation, automobile fuels by the year 2000 are likely to consist of gasoline, methanol from coal, diesel oil and liquefied petroleum gas, with only a small percentage of ethanol derived from biomass .―Gasohol,‖ used widely during the energy crisis of the 1970s in the United States, is a blend of 10 percent ethanol with 90 percent gasoline. The alcohol production process involves three steps: reduction of the material to water-soluble sugars, fermentation to produce alcohol, and distillation by boiling to separate the alcohol from the water . Considerable applied science and social research went into alcohol development as an alternative source of energy. Brazil and other countries actually became committed to full-scale production, with mixed results . For a number of reasons, the energy crisis abated by the 1980s, and the avenue of alternative fuels was de-emphasized in the U.S. Nevertheless, certain discoveries were made . Alcon Biotechnology, a joint venture between John Brown Engineers and Allied Breweries, developed a continuous fermentation process that could be housed in a standard shipping container . The process appealed to and gained approval in countries such as the Philippines, which had been trying to produce more fuel alcohol to offset growing oil import bills. Although significant sales of the new process did not materialize, the process may revive if oil price rise significantly. Fermented fuel from biomass has made headway in a few parts of the world, and other processes, such as production from waste products, are being investigated by biotechnology companies. Biomechanics, Inc ., for example, was one of the first companies to become involved in anerobic waste treatment technology. Anaerobic digestion of wastes takes place in the absence of air and results in the conversion of organic matter, by bacterial action, into a useful mixture of methane and carbon dioxide . In this process, over 93 percent of the effluent is converted into gas, leaving 3 percent as sludge, which is more efficient than the comparable biomass conversion into alcohol . The first commercial bioenergy plant was built in Ashford, Kent, England, by RHM, and was followed by a second facility in Bordeaux, France . As part of a continuing development program, five mobile plants have been sited at industrial locations in the United Kingdom. They were used to tread effluents from dairy, cider, pectin, confectionary, yeast, brewing, distilling, and chemical plants. In Italy, the process was used to treat effluents from cheese and ham processing, and in Spain, in slaughterhouse, operations. Savings on water charges for effluents treatment and energy saving derived from used of the 29 methane show that a bioenergy plant can make a financial profit not realized through aerobic treatment, as well as satisfy statutory requirements for disposal of waste . In the U.S., firms like BioTechnica have been examining methods in which landfill waste-disposal sites can be converted into ―bioreactors‖ for methane production. Many landfills take in 5,000 tons of refuse everyday. One percent of the national energy need could be satisfied by this type of process. The new concept envisions designing the landfill site from scratch as a bioreactor, with gas production as the basic objective. Although the overall energy contribution is likely to be small, the magnitude of the national requirement makes the technology important. Another viable route for energy production appears to be in developing enzymes, like cellulase, which break down cellulose. An estimated billion tons of cellulose that could be converted into chemical energy goes to waste in the U.S. each year. The gene that codes for cellulase has been isolated by scientists at Cornell University and grown in large quantities by E. coli . Although still in the development stages, the finding shows how rDNA technology can eventually transform biofuel production. The energy crisis of the 1970s produced many new ideas about energy generation, one example being photobiological generation, the production of hydrogen by whole microorganisms. Before support for this approach was reduced by the Reagan administration in the 1980s, a number of photosynthetic bacteria nonphotosynthetic bacteria, cyanobacteria, and green, red, and brown algae were discovered. These organisms produced the enzyme hydrogenase, which is necessary to make hydeogen. Professor David Hall of King’s College, London, believes that such a system could supply the word’s current energy needs using 0.5 million square kilometers (0.1 percent of the earth’s surface, an area about the size of France). If fossil fuel reserves become depleted, these energy alternatives may become future realities. Whether the farmer or rural areas will benefit by this possibility depends on the methods actually employed and their location. 30 Lesson 15 New Foods and Food Producers The new fermentation applications of biotechnology are resulting in new foods and new food producers, as well as sophisticated refinements throughout the existing production process. This development is not restricted to the United States, but is a worldwide trend. Scotland, a large producer of whiskey, is now being challenged by Japan. However, Scottish entrepreneurs are responding to the Japanese rivalry by creating a new, competitively priced soy sauce. Biotechnology will probably play an expanded role in the refinement of conventional fermentation processes involving dairy products, beverages, cocoa, and the development of new strains of bacteria and yeasts. Yet, there is a bias among the biogenetic companies against the food and drink markets because the profit margins are considerably less than in pharmaceuticals. Any new product will be viewed by licensing authorities as new and novel and, therefore, will be subject to the same costly approval procedures as pharmaceuticals. Biotechnology can shorten certain time spans that will benefit the food industry. The new tests for Salmonella, for example, pinpoint food contaminants, frequently in less than 36 hours, which is an improvement of several days over the older methods. A commercially available enzyme can reduce the ripening period for cheese-making by 2 months (about a third) for cheddar cheese. The savings are projected at more than $50 million annually for the industry, once the enzyme is further refined and becomes acceptable to cheese-makers. Toxicity testing of such enzymes, as required by Federal regulations, has caused concern within the industry. The process for regulatory clearance is still new. A possible test case has emerged with a genetically engineered rennin in cheese produced by Genencor, a joint venture between Genentech and Corning Glass Works. Genencor completed the world's first large-scale trials of cheeses made with rennin produced by genetically engineered bacteria in the 1980s. The product is comparable in flavor and texture with the naturally created cheese, and possesses the advantage of production in unlimited quantities. Unlike rennin made from the stomachs of calves, the new product would be acceptable to vegetarians. Another U.S. biotechnology company, Collaborative Research, received the first British patent for recombinant rennin 31 in 1984, which the company claimed to be the first patent on rennin as well as the first patent on an industrial enzyme. Other biotechnology firms are seeking salable bioproducts of cheese making. Whey, for example, has received considerable interest as a source of protein, a flavor-enhancer, binder in hamburgers, and substitute for egg whites in baking, although the cost has yet to become competitive. Costs in the health and diet markets, however, are not as critical. Another byproduct of whey is methane gas. Eight thousand tons of cheese will produce about 80,000 tons of whey waste, from which 300 tons of protein can be extracted and a volume of methane gas equivalent to 600 tons of oil. In Wales, a biotechnology is concentrating on novel uses of Welsh milk in yogurt and in production of a milk liqueur to rival Bailey's Irish Cream, which currently commands the British liqueur market. In an experimental stage within the Champagne region of France, work is underway on a faster champagne production process. Yeasts are encapsulated in a gelatinous membrane so that the sediments can be removed more easily. If this is accomplished properly, many filtration steps and subsequent losses of liquid will be eliminated. Costs will be cut dramatically, but at no loss in the quality of the product. Brewing industries worldwide have embarked on biotechnology research as much to ensure survival as to find new profitable products. United Breweries of Denmark (composed of Carlsberg and Tuborg) launched Carlsberg Biotechnology in 1982 to develop new technologies and to commercialize enzymes and other products involved in the brewing process. New yeasts are being developed that are tailored to the barley and hops of different regions of the world. The U.K. Brewing Research Foundation is one of a number of organizations developing diet beers. They are working with new yeast strains that break down dextrin compounds and produce a low-carbohydrate, low-calorie brew. Yeast fusion techniques or rare mating, the crossing of normal brewing strains with mutant strains that will not fuse in the normal way have potential for the brewing industry. Many of these traditional fermentation industries are not only making products for themselves, but are diversifying into new areas. Allied Breweries of the United Kingdom, for example, attempted to market a continuous fermentation process, originally developed for beer production, aimed at the fuel-alcohol market. In the 32 United States, a number of new bio-startup companies are funded by brewers like Adolph Coors, which is trying to develop new metal-cleaning products expected to be environmentally safer than the existing chlorinated products. As pharmaceutical firms have moved into agricultural products, some brewers are venturing into pharmaceuticals. Anheuser-Busch signed an agreement in 1983 with Interferon Sciences to develop yeasts for recombinant interferon production. Kirin, one of Japan's leading brewers, entered into a joint venture with Amgen to develop and market the hormone erythropoietin, while Suntory has the marketing rights in Japan for Schering-Plough's gamma interferon. Dairy companies like Snow Brand and Meiji Milk are moving into medical biotechnology. Snow brand is making the transition to medical biotechnology by way of health foods and foods with some medical effect. Snow brand already sells milk products for people who cannot tolerate the milk ingredients phenylalanine and histidine. The company is developing products designed for heart disease and cancer patients, and is also moving into plant biotechnology. Specialty businesses, such as spice companies, are investing funds in biotechnology to improve production. New foods and drinks that will be available by the turn of the century or sooner may not even be currently imaginable. Consumers will probably not know that biotechnology is involved in their diet. While the manufacturer may stress the natural aspect of the product, it is unlikely that genetic engineering will be mentioned on the product label. Tomatoes, for example, may look and taste alike, but with the cloning of the ripening gene, they are apt to be different from those grown yesterday and today. 33 Lesson 16 Blazing a Genetic Trail in Medicine The miraculous substance that contains all of our genetic instructions, DNA, is rapidly becoming a key to modern medicine. By focusing on the diaphanous and extraordinarily long filaments of DNA that we inherit from our parents, scientists are finding the root causes of dozens of previously mysterious diseases: abnormal genes. These discoveries are allowing researchers to make precise diagnoses and predictions, to design more effective drugs, and to prevent many painful disorders. The new findings also pave the way for the development of the ultimate therapy - substituting a normal gene for a malfunctioning one so as to correct a patient's genetic defect permanently. Recently, scientists have made spectacular progress against two fatal genetic diseases of children, cystic fibrosis and Duchenne muscular dystrophy. In addition, they have identified the genetic flaws that predispose people to more widespread, though still poorly understood ailments - various forms of heart disease, breast and colon cancer, diabetes, arthritis - which are not usually thought of as genetic in origin. While many of the researchers who are exploring our genetic wilderness want to find the sources of the nearly 4,000 disorders caused by defects in single genes, others have an even broader goal: They hope to locate and map all of the 50,000 to 100,000 genes on our chromosomes. This map of our complete biological inheritance "the marvelous message, evolved for 3 billion years or more, which gives rise to each one of us," as Robert Sinsheimer of the University of California, Santa Barbara, calls it - will guide biological research for years to come. And it will radically simplify the search for the genetic flaws that cause disease. Once scientists have identified such a flaw, they need to understand just how it produces a particular illness. They must determine the normal gene's function in human cells: What kind of protein does it instruct the cells to make, in what quantities, at what times, and in what specific places? Then the researchers can ask whether the genetic flaw results in too little protein, the wrong kind of protein, or no protein at all - and how best to counteract the effects of this failure. For most genetic disorders, researchers are still at the very beginning of the trail. They have no clues to the DNA error that causes a disease, and they are still trying to find large families whose DNA patterns can help them track it down. By contrast, scientists who work on cystic fibrosis and a few other diseases have covered much of the trail. They have already succeeded in correcting the gene defect inside living human cells by inserting healthy genes into these cells in a laboratory dish - an achievement that may lead to gene therapy. 34 The farther scientists go along the trail, the broader the implications of their findings. For example, the discovery of the gene defect that causes Duchenne muscular dystrophy, a muscle-wasting disease, led scientists to identify a previously unknown protein that plays an important role in all muscle function. This gives them a clearer view of how muscle cells work and allows them to diagnose other muscle disorders with exceptional precision, as well as devise new approaches to treatment. Any new treatment will need to be tested on animals. In fact, the next explosion of information in medical genetics is expected to come from the study of animals - particularly with defects that mimic human disorders. The techniques for producing animal models of disease are improving rapidly. Even today, "designer mice" are playing an increasingly important role in research. The growth of powerful computerized databases is bringing further insights. Only a month after the discovery of the genetic error involved in neurofibromatosis, a disfiguring and sometimes disabling hereditary disease, a computer search revealed a match between the protein made by normal copies of the newly uncovered gene and a protein that acts to suppress the development of cancers of the lung, liver, and brain - a key finding for cancer researchers. Such revelations are becoming increasingly frequent. "If a new sequence has no match in the databases as they are, a week later a still newer sequence will match it," observes Walter Gilbert of Harvard University. Brain disorders such as schizophrenia or Alzheimer's disease may be next to yield to the genetic approach. "We won't know what went wrong in most cases of mental disease until we can find the gene that sets it off," says James Watson, co-discoverer of the structure of DNA. Progress in medical genetics is picking up speed. Every day, more pieces of the puzzle fall into place. As a harried but exultant geneticist declared at a scientific meeting recently, "This is a very exciting time. . . I encourage you to stay tuned." 35 Reading materials Passage 1 Biology is a fascinating and important subject, because it dramatically affects our daily lives and our futures. Many biologists are working on problems that critically affect our lives, such as the word’s rapidly expanding population and diseases like cancer and AIDS. The knowledge these biologists gain will be fundamental to our ability to manage the world’s resources in a suitable manner, to prevent or cure diseases, and to improve the quality of our lives and those of our children and grandchildren. Biology is one of the most successful of the ―natural sciences‖, explaining what our world is like. To understand biology, you must first understand the nature of science. The basic tool a scientist uses is thought. To understand the nature of science, it is useful to focus for a moment on how scientists think. They reason in two ways: deductively and inductively. Passage 2 The history of life on earth has been a history of interaction between living things and their surroundings. To a large extent, the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time, the opposite effect, in which life actually modifies its surroundings, has been relatively slight. Only in the present century has one species--man acquired significant power to alter the nature of his world. During the past quarter century this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air, earth, rivers, and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable. In this now universal contamination of the environment, chemicals are the sinister partners of radiation in changing the very nature of the world, the very nature of its life. It took hundreds of millions of years to produce the life that now inhabits the earth. Given time not in years but in millennia life adjusts, and a balance has been reached. But in the modern world there is no time. It is not my contention that chemical insecticides must never be used. I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons, without their consent and often without their knowledge. I contend, further more, that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil, water, wildlife, and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life. 36 Passage 3 Scientists have recently estimated that approximately 30 to 40 percent of all cancers could be averted if people ate more fruits, vegetables, and plant-based foods and minimized high-fat, high-calorie that have scant nutritional value. Up to 70 percent of cancers might be eliminated if people also stopped smoking, exercised regularly, and controlled their weight. In the past, researchers had linked fat consumption with the development of cancers, but they currently believe that eating fruits, vegetables, and grains may be more important in preventing the disease than not eating fat. ― the evidence about a high-fat diet and cancer seemed a lot stronger several years ago than it does now,‖ says Melanie Polk, a registered dietitian and director of nutrition education at the American Institute for Cancer Research. Although scientists are still not certain about the specifics, they are beginning to close in on the healthful constituents of plant-based foods. In particular, they are looking closely at two components-antioxidants and phytochemicals. Passage 4 Biology literally means ―the study of life‖ .Biology is such a broad field, covering the minute workings of chemical machines inside our cells, to broad scale concepts of ecosystems and global climate change. Biologists study intimate details of the human brain, the composition of our genes, and even the functioning of our reproductive system. Biologists recently all but completed the deciphering of the human genome, the sequence of deoxyribonucleic acid (DNA) bases that may determine much of our innate capabilities and predisposition to certain forms of behavior and illnesses. DNA sequences have played major roles in criminal cases (O. J . Simpson, as well as the reversal of death penalties for many wrongfully convicted individuals), as well as the impeachment of President Clinton (the stain at least did not lie). We are bombarded with headlines about possible health risks from favorite foods (Chinese, Mexican, hamburgers, etc.) as well as the potential benefits of eating other foods such as cooked tomatoes. Informercials tout the benefits of metabolism-adjusting drugs for weight loss. Many Americans are turning to herbal remedies to ease arthritis pain, improve memory, as well as improve our moods. Robert Hooke (1653-1703), one of the first scientists to use a microscope to examine pond water, cork and other things, referred to the cavities he saw in cork as ―cells‖, Latin for chambers. Mattias Schleiden (in 1838) concluded all plant tissues consisted of cells. In 1839, Theodore Schwann came to a similar conclusion for animal tissues. Rudolf Virchow, in 1858, combined the two ideas and added that all cells come from pre-existing cells, formulating the Cell Theory. Thus there is a chain-of-existence extending from your cells back to the earliest cells, over 3.5 billion years ago. The cell theory states that all organisms are composed of one or more cells, and that those cells have arisen from pre-existing cells. In 1953, James Watson and Francis Crick developed the model for deoxyribonucleic acid (DNA), a 37 chemical that had (then) recently been deduced to be the physical carrier of inheritance. Crick hypothesized the mechanism for DNA replication and further linked DNA to proteins, an idea since referred to as the central dogma. Information from DNA ―language‖ is converted into RNA (ribonucleic acid ―language‖ and then to the ―language‖ of proteins. The central dogma explains the influence of heredity (DNA) on the organism (proteins). Homeostasis is the maintenance of a dynamic range of conditions within which the organism can function. Temperature, pH and energy are major components of this concept. Thermodynamics is a field of study that covers the laws governing energy transfers, and thus the basis for life on earth. Two major laws are known: the conservation of matter and energy, and entropy. The universe is composed of two things: matter (atoms, etc.) and energy. These first three theories are very accepted by scientists and the general public. The theory of evolution is well accepted by scientists and most of the general public. However, it remains a lightening rod for school board, politicians, and television preachers. Much of this confusion results from what the theory says and what it does not say. Passage 5 New research on dolly, the cloned sheep, hints that young clones might not mark time like the rest of us from birth. Instead, 3-year-old Dolly may be aging like the now 9-year-old donor from which she was cloned. The evidence lies in telomeres, bits of DNA that cap the ends of chromosomes and contract over time, as cell divide, scientists believe that once telomeres hit a certain length, the cell stops proliferating and eventually dies; some argue that this ―cellular senescence ‖triggers aging. when Scottish scientists, led by Paul Shiels of PPL Therapeutics, examined Dolly’s telomeres, the found that they were 20 percent shorter than expected ,similar in length to those of her 9-year-old ― parent ‖. The finding were published in last week’s Nature. But Biologists note that telomere length varies among creatures and is hard to measure. More–over, because of the study’s tiny sample (one sheep cloned from an adult), it remain to be seen whether other cloned mammals will have short telomeres. If they do, that would deal yet another blow to the science of cloning, which is plagued by puzzlingly high rates of death and diseases (U.S News, May 24, 1999). Cloning a beloved great-aunt or oneself (impossibilities at this state ) might not breed immortality ,just old clones. But Dolly ― isn’t older in how we think of sheep aging, ‖ saying Tom Cech, a telomere researcher at the University of Colorado-Boulder. He says that Dolly seems a typical 3-year-olds and has given birth to several healthy offspring, at least one of whom has normal-length telomeres. Old-fashioned conception just might reset the telomeric clock . 38 Passage 6 Years ago, the bacteria Agrobacterium tumefaciens was thought to exist anywhere in soil. Later discoveries found that it was associated with plant roots. It is Gram-negative, rod-shaped, aerobic and can easily infect virtually any dicot plant. It was originally thought to have peritrichous flagella, but later understood to have 5-11 circumtrichetal flagella. Optimum growth occurs at 32? with a trace of manganese and succinate serving as the carbon source. A. tumefaciens infects the roots of plants at the site of mechanical injury. The injury signals the production of lignin precursors, which in turn induce the vir genes of A. tumefaciens. These genes carry out the transformation process whereby the A. tumefaciens genes are incorporated into the plant’s genome. This transformation causes crown gall disease, which leads to tumor overgrowths on the surface of plant roots. The infection does not result in plant death, merely altered cell function. A. tumefaciens carries the vir gene on its Ti plasmid. Each gene controls a different aspect of the infection. VirB encodes transmembrane mediators, virE controls single-strand DNA binding, virF affects infection efficiency, and virG contains the transcriptional regulator. Other genes control other aspects of infection, but have not been completely characterized yet. As a result of its ability to manipulate genetic material, A. tumefaciens has been useful in the introduction of exogenous genes into host plant cells. By far the most interesting aspect of A. tumefaciens is the ability to transfer its genes into the plant’s genome. The infected cells then produce opines, which serve as sources of nitrogen and carbon. A. tumefaciens also contains genes for the catabolism of opines, but these are not transferred to the plant. This allows only the bacteria to digest opines, with a steady non-digested stream manufactured by the plant. Passage 7 What is gene therapy? Genes, which are carried on chromosomes, are the basic physical and functional units of heredity. Genes are specific sequences of bases that encode instructions on how to make proteins. Although genes get a lot of attention, it’s the proteins that perform most life functions and even make up the majority of cellular structures. When genes are altered so that the encoded proteins are unable to carry out their normal functions, genetic disorders can result. Gene therapy is a technique for correcting defective genes responsible for disease development. Researchers may use one of several approaches for correcting faulty genes: A normal gene may be inserted into a nonspecific location within the genome to replace a nonfunctional gene. This approach is most common. An abnormal gene could be swapped for a normal gene through homologous recombination? The abnormal gene could be repaired through selective 39 reverse mutation, which returns the gene to its normal function. The regulation (the degree to which a gene is turned on or off) of a particular gene could be altered. Passage 8 Scientists have known since 1952 that DNA is the basic stuff of heredity. They've known its chemical structure since 1953. They know that human DNA acts like a biological computer program some 3 billion bits long that spells out the instructions for making proteins, the basic building blocks of life. But everything the genetic engineers have accomplished during the past half-century is just a preamble to the work that Collins and Anderson and legions of colleagues are doing now. Collins leads the Human Genome Project, a 15-year effort to draw the first detailed map of every nook and cranny and gene in human DNA. Anderson, who pioneered the first successful human gene-therapy operations, is leading the campaign to put information about DNA to use as quickly as possible in the treatment and prevention of human diseases. What they and other researchers are plotting is nothing less than a biomedical revolution. Like Silicon Valley pirates reverse-engineering a computer chip to steal a competitor's secrets, genetic engineers are decoding life's molecular secrets and trying to use that knowledge to reverse the natural course of disease. DNA in their hands has become both a blueprint and a drug, a pharmacological substance of extraordinary potency that can treat not just symptoms or the diseases that cause them but also the imperfections in DNA that make people susceptible to a disease. And that's just the beginning. For all the fevered work being done, however, science is still far away from the Brave New World vision of engineering a perfect human—or even a perfect tomato. Much more research is needed before gene therapy becomes commonplace, and many diseases will take decades to conquer, if they can be conquered at all. In the short run, the most practical way to use the new technology will be in genetic screening. Doctors will be able to detect all sorts of flaws in DNA long before they can be fixed. In some cases the knowledge may lead to treatments that delay the onset of the disease or soften its effects. Someone with a genetic predisposition to heart disease, for example, could follow a low-fat diet. And if scientists determine that a vital protein is missing because the gene that was supposed to make it is defective, they might be able to give the patient an artificial version of the protein. But in other instances, almost nothing can be done to stop the ravages brought on by genetic mutations. Passage 9 Most people think of lions as strictly African beasts, but only because they’re been killed off almost everywhere else. Ten thousand years ago lions spanned vast sections of the globe. Now lions hold only a small fraction of their former habitat, and Asiatic lions, a subspecies that spit from African lions perhaps 100,000 years ago, hang on to an almost impossibly small slice of their former territory. 40 India is the proud steward of these 300 or so lions, which live primarily in a 560-square-mile sanctuary. It took me a year and a half to get a permit to explore the entire Gir Forest---and no time at all to see why these lions became symbols of royalty and greatness. A tiger will hide in the forest unseen, but a lion stands its ground, curious and unafraid---lionhearted. Though they told me in subtle ways when I got too close, Gir’s lions allowed me unique glimpses into their lives during my three months in the forest. It’s odd to think that they are threatened by extinction; Gir has as many lions as it can hold----too many, in fact. With territory in short supply, lions move about near the boundary of the forest and even leave it altogether, often clashing with people. That’s one reason India is creating a second sanctuary. There are other pressing reasons: outbreaks of disease or natural disasters. In 1994 a serious disease killed more than a third of Africa’s Serengeti lions----a thousand animals----a fate that could easily happen to Gir’s cats. These lions are especially vulnerable to disease because they descend from as few as a dozen individuals. ―If you do a DNA test, Asiatic lions actually look like identical twins,‖ says Stephen O’Brien, a geneticist who has studied them. Yet the dangers are hidden, and you wouldn’t suspect them by watching these lords of the forest. The lions display vitality, and no small measure of charm. Though the gentle intimacy of play vanishes when it’s time to eat, meals in Gir are not necessarily frantic affairs. For a mother and her baby lion sharing a deer, or a young male eating an antelope, there’s no need to fight for a cut of the kill. The animals they hunt for food are generally smaller in Gir than those in Africa, and hunting groups tend to be smaller as well. Passage 10 When a scottish research team startled the world by revealing 3 months ago that it had cloned an adult sheep, President Clinton moved swiftly. Declaring that he was opposed to using this unusual animal husbandry technique to clone humans, he ordered that federal funds not be used for such an experiment although no one had proposed to do so and asked an independent panel of experts chaired by Princeton President Harold Shapiro to report back to the White House in 90 days with recommendations for a national policy on human cloning. That group the National Bioethics Advisory Commission has been working feverishly and at a meeting on 17 May, members agreed on a near-final draft of their recommendations. NBAC will ask that Cliton’s 90-day ban on federal funds for human cloning be extended indefinitely, and possibly that it be made law. But NBAC members are planning to word the recommendation narrowly to avoid new restrictions on research that involves the cloning of human DNA or cells routine in molecular biology. The panel has not yet reached agreement on a crucial question, however, whether to recommend legislation that would make it a crime for private funding to be used for human cloning. In a draft preface to the recommendations, discussed at the 17 May meeting, Shapiro suggested that the panel had found a broad consensus that it would be ―morally unacceptable to attempt to create a 41 human child by adult nuclear cloning‖. Shapiro explained during the meeting that the moral doubt stems mainly from fears about the risk to the health of the child. The panel then informally accepted several general conclusions，although some details have not been settled. NBAC plans to call for a continued ban on federal government funding for attempt to clone body cell nuclei to create a child. Because current federal law already forbids the use of federal funds to create embryo’s life, NBAC will remain silent on embryo research.. NBAC members also indicated that they will appeal to privately funded researchers and clinics not to try to clone humans by body cell nuclear transfer. But they were divided on whether to go further by calling for a federal low that would impose a complete ban on human cloning. Shapiro and most members favored an appeal for such legislation, but in a phone interview, he said this issue was ―up in air‖. Passage 11 The Pure Food Campaign was launched by environmental activist Jeremy Rifkin and others in direct response to the FDA announcement. They demanded that the FDA undertake mandatory premarket testing of all genetically engineered foods, label them, and require premarket public notification by all manufacturers of the presence of such goods in stores, so that the foods could be traced if illnesses or other problems arose. The prominent New York restaurant chefs who joined the controversial Rifkin at a press conference in June 1992 affirmed their support for what the organizers hoped would be an international boycott, when and if genetically engineered good enters the marketplace. As one chef put it, I will not sacrifice the entire history of culinary art to revitalize the biotechnology industry. Where does the truth lie Or rather, is there a truth that we can discern while trying to distinguish between face and fantasy The only way to find out is to look at the record of actions as well as words, and listen to the arguments. It is difficult, however, to be a completely impartial observer of the struggle to balance profit making with risk taking. The abundance, variety, quality, and safety of the worlds food supply affect each of us and all our descendants. Biotechnology is driven by economics. So far, because of the availability of the necessary genes, as well as market demands, most agricultural biotechnology research and development has centered on the genetic modification of plants to create varieties that are resistant to herbicides, insects, and plant diseases, have a longer shelf life, and reduce processing costs. Such plants will be valuable commodities. Given the profit motive, it is perfectly logical that the first transgenic plant headed for market is the Flavr Savr tomato and not a high protein crop for the worlds impoverished hungry. Calgene, Inc., invested $20 This is simply a model of private enterprise at work. It should be no surprise to anyone who has ever 42 bought a new car model or the latest computer. However, among the serious concerns raised about this situation is the notion that the economic incentives to create, develop, test, and market genetically engineered organisms have created a climate in which the health of the environment as well as individuals could be seriously threatened, perhaps in ways that may be irreversible. Passage 12 Until recently, the "science of the future" was supposed to be electronics and artificial intelligence. Today it seems more and more likely that the next great breakthroughs in technology will be brought through a combination of those two sciences with organic chemistry and genetic engineering. This combination is the science of biotechnology. Organic chemistry enables us to produce marvelous synthetic materials(However, it is still difficult to manufacture anything that has the capacity of wool to conserve heat and also to absorb moisture(Nothing that we have been able to produce so far comes anywhere near the combination of strength 1ightness and flexibility that we find in the bodies of ordinary insects. Nevertheless, scientists in the laboratory have already succeeded in "growing" a material that has many of the characteristics of human skin. The next step may well be "biotech hearts and eyes" which can replace diseased organs in human beings. These will not be rejected by the body, as is the case with organs from humans. The application of biotechnology to energy production seems even more promising(In 1996 the famous science(fiction writer，Arthur C(Clarke，many of whose previous predictions have come true, said that we may soon be able to develop remarkably cheap and renewable sources of energy(Some of these power sources will be biological. Clarke and others have warned us repeatedly that sooner or later we will have to give up our dependence on non-renewable power sources. Coal, oil and gas are indeed convenient. However, using them also means creating dangerously high levels of pollution. It will be impossible to meet the growing demand for energy without increasing that pollution to catastrophic levels unless we develop power sources that are both cheaper and cleaner. It is attempting to think that biotechnology or some other "science of the future" can solve our problems(Before we surrender to that temptation we should remember nuclear power(Only a few generations ago it seemed to promise limitless，cheap and safe energy. Today those promises 1ie buried in a concrete grave in a place called Chernobyl, in the Ukraine. Biotechnology is unlikely. however, to break its promises in quite the same or such a dangerous way. 43