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Trial Version Case Study: Gene, gene cloning and biotechnology Key Concept: Overview of Gene and Nucleic Acids Structure of DNA, DNA Sequences and Restriction Enzyme Introduction of Gene Cloning, Genetic Engineering and Biotechnology Ethnical, social and economical issues in Biotechnology and Gene Therapy Materials Preparation: Prior to the class, search information, such as news articles relating to gene, gene cloning and biotechnology. Suggested activities: 1. Have a class discussion about genes. Explain that genes are inherited from parents and are important because they determine much about behavioral, mental, and physical traits. Every gene contains a DNA (deoxyribonucleic acid) code that gives the cell instructions about how to make specific proteins. These proteins form the basis for the structural framework of life. 2. Encourage students to discuss on the following: 1. Issues on the new genetic research – students may write their ideas on a large sheet of newsprint, discuss cloning animals, using DNA in criminal investigations, or gene therapy for some types of genetic diseases and cancer. 2. Issues on biotechnology, gene cloning and genetic engineering. For example, the technology may allow a 60-year-old woman to have a baby. Is that a positive or negative outcome? Consider its ramifications. 3. It took scientists 277 attempts to clone a normal, healthy sheep (Dolly). But what happened to the other 276 sheep? Encourage students to research these previous attempts and ask them to think about the consequences of cloning. 4. Have students brainstorm the risks and benefits associated with biotechnology. For example, the removal of hemophilia or other serious disorders from the gene pool is a benefit because people would no longer suffer from a chronic condition. An example of a risk is going too far in selecting the genetic makeup of future children. Possible risks: Selection of the genetic makeup of future children. This practice may give people the power to control some personal traits, such as having blond hair or being tall. Taken to an extreme, this could eliminate some traits. Using biotechnology before exploring other options, particularly in reproductive medicine. For example, technology enables scientists to implant an egg from one woman into the uterus of another. But it may not be a good idea to use this technique before trying less extreme techniques first. 1 Trial Version Possible benefits: Eliminating genetic diseases. For example, geneticists think it may be possible to eliminate genetic diseases such as Tay-Sachs through careful and methodical screening programs. Screening unborn babies. This refers to screening for genetic disorders either before a pregnancy takes place or in the early months of a pregnancy. More information would give prospective parents more options in dealing with their infants’ problems. Treating diseases. For example, scientists are working on ways to insert cells from embryos into cancerous cells as a way to stop the growth of cancer. Reference: 1. http://www.accessexcellence.org/AE/AEPC/BE02/gentest/fail15.html? Cloning Genetic Science Learning Center “Teacher resources” – (http://gslc.genetics.utah.edu/teachers/) 2. Biotechnology – (www.zoo.ufl.edu/PCB3063/biotech handout.pdf) 3. Molecular Genetics – (http://fig.cox.miami.edu/~cmallery/150/gene/mol_gen.old.htm) 4. Cloning Fact Sheet – (http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml#whatis) 5. What is Biotechnology – (www.aitc.ca/bc/media/BioTechS1.pdf) 6. Biotech Kids Carnival – (http://www.swmed.edu/stars/resources/stock02/Riddle.doc) 7. AACAES : Educators : Science Activities – (http://www.uga.edu/discover/educators/environmental_science/activities/qcc34.ht ml) / (http://www.uga.edu/discover/educators/applied_bio_chem_2/all/all10.html) 8. Isolation DNA – (http://fog.n4h.org/f33.htm) 9. A Feast For Our Future – (http://www.accessexcellence.org/AE/AEPC/WWC/1992/transgenic_food.html) Prepare notes and questions to be discussed before the session: Level of difficulties: [1] Prior concepts [2] Essential concepts [3] Big and global concepts 2 Trial Version 1. Discovery of inheritance [1] The mechanism of inheritance was discovered by Gregor Mendel (1822-1884), an Austrian monk who crossed different pea plants and noted the manner in which different characteristics of coloring, of seed appearance, of length of stem were developed. This led to the proposal of “the Mendelian laws of inheritance.” However, he did not know the factors responsible for inheritance. For details, visit: Gregor Mendel – (http://www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.html) (Photo adapted from: http://tidepool.st.usm.edu/crswr/103inheritance.html http://www.uwinnipeg.ca/~simmons/cm1503/mendel.htm) 2. In the early twentieth century, it became clear the factors were something called “genes” which were found in chromosomes in the nucleus of a cell. [Now, it is known that genes are made up of deoxyribonucleic acid (DNA) packaged in compact units in chromosomes. One strand of DNA, approximately 3 meters long, contains many genes. All these genes give instructions for how to make and operate (Photo adapted from: the parts in our body.] http://www.toyamampu.ac.jp/ph/yakka/research/p3.html) Gene and nucleic acids In 1869, Friedrich Miescher, a German chemist, found a “new” class of acid substance from pus cells (also salmon sperm heads) that was not carbohydrate, lipid, or protein. (At that time, organic substances were classified into these three broad groups.) Since the substance was isolated from nuclei, it was later named nucleic acid. In around 1910, it was found that nucleic acid contained two purines adenine (A) and guanine (G), and two pyrimidines, thymine (T) and cytosine (C), all in equimolar amounts. These are called bases. 3 Trial Version In the mid twentieth century, both circumstantial and direct evidence suggested the role of deoxyribonucleic acid (DNA) in heredity. It is now known that DNA is the genetic material except in the case of certain viruses which do not contain DNA. In such viruses the genetic information is contained in ribonucleic acid (RNA). All nucleic acids contain three components: a base and a sugar with a phosphate attached to it. RNA differs from DNA in two major aspects: (a) RNA contains uracil instead of thymine, and (b) the sugar is a ribose instead of a deoxyribose. Now it is clear that a gene is a DNA sequence. A gene is a linear sequence of DNA that contains all information necessary for the production of a protein and different types of RNA. In human, there are 46 chromosomes (22 pairs of autosomal chromosomes and 2 sex chromosomes, X and Y). They house almost 3 billion base pairs of DNA that contains about 30,000 - 40,000 protein-coding genes. The coding regions make up less than 5% of the genome (the function of the remaining DNA is not clear) and some chromosomes have a higher density of genes than others. 3. Structure of DNA [1] In 1953, Wilkins, MHF and associates based on their x-ray diffraction (a technique that enable molecular biologists to construct the 3-dimensional structure of a molecule) study proposed that a DNA molecule contained helical chains, like a twisted ladder. In the same year, Watson JD and Crick FHC, based on their and other scientists’ biochemical findings, proposed the double-helix model of DNA in which A paired specifically with T, and G with C. The means that the two strands are complimentary and that the nucleotide sequence on one strand determines that on the other. O OH P - O O HO H2C O O A T O CH2 O O O H2C CH2 O O H2C O O O CH2 O O P O O A O T O HO - O O H2C O G C P - O P O O - O P O O C G O O - O P O O - O P - CH2 - O O P OH 4 O Trial Version Some basic features of DNA and RNA DNA a double stranded helix “rungs’ in the ladder of the helix joined together by hydrogen bonds phospodiester linkages between 5’ & 3’ ends of nucleotides; 5’ 3’ direction contains deoxyribose sugar contains A, T, C, G nucleotides found in the nucleus of cells; some is found in the mitochondria RNA primarily a single stranded molecule linked by the same type of phosphodiester bonds that join DNA together; 5’ 3’ direction contains ribose sugar contains A, U, C, G nucleotides 3 types of RNA – messenger, ribosomal & transfer (mRNA, rRNA, tRNA) found in the cytoplasm; however it is manufactured in the nucleus, so some is found there Most naturally occurring DNA molecules are so long that to determine the sequence of the whole molecule in one operation would be unthinkable. For example, there are about 4 x 106 base pairs in the entire genetic content of Escherichia coli (E. coli), an intestinal bacterium. (For detail about DNA, genes and chromosomes visit: Tour of the Basic (http://gslc.genetics.utah.edu/units/basics/tour/) 4. DNA sequencing [2,3] In order to decode the secret information stored in a DNA molecule, it is necessary to find out the sequence of bases in it. Because DNA is such a long molecule, how do we know where is the head? Where is the tail? Fortunately, there are restriction endonucleases which cleave DNA at specific base sequence they recognize, hence named restriction enzymes. An endonuclease is a pair of DNA scissors that catalyzes (hydrolytic) cleavage of a DNA molecule at specific base sequence. For example, HaeIII, a restrict enzyme, cleaves in the middle of the sequence …..GG↓CC….. and no where else. BamHI makes a cut at G↓GATCC and PstI at CTGCA↓G. Whenever this sequence occurs, this enzyme will make a cut. At present, hundreds of restriction enzymes have been isolated and many of them are commercially available. By using different enzymes (or enzyme combinations), we can obtain pieces of shorter DNA fragments. By arranging these fragments, we can deduce the base sequence in a DNA molecule. 5 Trial Version 5. Why do bacteria produce restriction enzymes? [2,3] Restriction enzymes are found in a wide variety of microorganisms and play vital defense role in bacterial cells. We know that viruses can infect a bacterial cell, if the cell contains a set of restriction enzymes that cut up foreign viral DNA into pieces and destroy it as soon as it enter the cell. The entry of such DNA would be “restricted.” Bacterial cells contain special chemically modified DNA to prevent the attack on the host DNA. 6. What is polymerase chain reaction (PCR)? [1,2] DNA polymerase is an enzyme that is able to replicate a DNA molecule in the cell nucleus. Replication of DNA requires DNA polymerase, a primer and nucleotides. PCR is a technique that is designed based on the DNA replication in cells to amplify the number of copies of a specific DNA sequence (or a gene) through cycles of denaturation (breaking the helix into separate chains) and replication in a test tube. Kary Banks Mullis was the inventor of PCR. For his invention of the PCR method, he won The Nobel Prize in Chemistry 1993. PCR is a key technique in molecular biology and biomedical fields that permits the analysis of any pieces of a short sequence of DNA without having to clone it. Before the invention of PCR, amplifying of genes or DNA was done in bacteria, and took weeks. But now with PCR, it takes only a few hours. Three steps are involved in a PCR. These 3 steps are repeated for 35 or 45cycles. The cycles are done in a machine called PCR machine or a thermo-cycler, which rapidly heats and cools the test tubes containing the reaction mixture. The 3 steps for one cycle take place at different temperatures and they are: 1. Denaturation: At 94°C, heat breaks the hydrogen bonds and the double-stranded DNA melts and opens into single-stranded DNA. 2. Annealing: At 54°C, hydrogen bonds form between the "primer" and the single-stranded DNA from samples. Primer is a short single-stranded DNA with known sequence designed by scientists to amplify a particular gene. The single-stranded DNA from samples is a template that provides the pattern to be copied. Since the number of primers is more than that of the long complimentary strand of the DNA, primers form hydrogen bonds with the single-stranded DNA from samples more easily than the long complimentary strand .We call this step as annealing. 6 Trial Version 3. Extension: After the annealing, the enzyme polymerase attaches to this double-stranded structure and starts copying the template. At 72°C, the polymerase works best. PCR is widely used in the biochemistry and molecular biology research, DNA fingerprinting and DNA sequencing. For animation of PCR in the Internet, visit: i. RT-PCR Methodology – (http://www.bio.davidson.edu/courses/Immunology/Flash/RT_PCR.html) ii. PCR animated – (http://users.ugent.be/~avierstr/principles/pcrani.html iii. Internet Resources – (http://www.woodrow.org/teachers/esi/2002/Biology/Projects/p3/pcrinternet.htm) 7. What is gene cloning? [1] A clone is a population of organisms that are genetically the same as they are derived from a single ancestor. For example, all of the bacteria in a colony on a culture plate are clones because they were derived from a single bacterium. To clone a gene generally means to use organisms to generate, through genetic engineering techniques, many copies of the specific gene in question or interest. Reference: i. Gene Cloning – (http://www.lsic.ucla.edu/ls3/tutorials/gene_cloning.html) ii. Gene Cloning (animation) – (http://croptechnology.unl.edu/download.cgi) iii. Human Cloning – (http://www.bbc.co.uk/science/genes/gene_safari/clone_zone/human_cloning.shtml) 8. How is a gene cloned? [2] First, with the help a restrict enzyme, one can isolate a DNA sequence containing a gene. Next, is to insert the gene into a vector (a carrier that would carry the gene into a host cell). The most commonly used vectors are plasmids or bacteriophages because they can replicate independently in a host cell, usually a bacterium like E.coli.. Gene Cloning Animation – (http://www.mybiology.com/archive_movies/dna_tech_movies.htm) 9. Since one can make copies of a DNA fragment by PCR, why do we still need to clone a gene? [2,3] PCR can only make copies of a small DNA fragment, but a gene is a very large fragment. So, it would be very difficult (or inefficient) when compared to what a cell can accomplish. Imagine if one wishes to obtain a large quantity of a particular protein (enzyme), one can simply insert the gene into bacteria to generate many copies of the gene. Also, they would do protein synthesis and we can collect the protein of interest later. 7 Trial Version PCR Animation: http://www.lsic.ucla.edu/ls3/tutorials/gene_cloning.html http://www.people.virginia.edu/~rjh9u/pcranim.html http://www.abpischools.org.uk/resources/poster-series/pcr/pcranim.asp http://www.rvc.ac.uk/Extranet/DNA_1/7_PCR.htm http://www.mybiology.com/archive_movies/dna_tech_movies.htm 10. What is genetic engineering? [1] By definition, genetic engineering is a scientific alteration of the structure of genetic material in a living organism. It involves the production and use of recombinant DNA and has been employed to create bacteria that synthesize insulin and other human proteins. Therefore, genetic engineering is a process that alters the genetic makeup of an organism. This technique provides remarkable opportunities to make a large quantity of protein, insulin for example, and to develop new medical procedures to treat diseases. In addition to revolutionizing some medical treatments, genetic engineering has much impact on food production, fuel industries, mining and pollution control. It has been said, the effects of genetic engineering to biotechnology is similar to microchips to information technology. Reference: i. Say no to genetic engineering – (http://www.greenpeace.org/international/campaigns/genetic-engineering) ii. Genetic engineering and its danger – (http://online.sfsu.edu/~rone/GEessays/gedanger.htm) iii. Genetic Engineering – look ma! no math! – (http://www.eurekascience.com/ICanDoThat/gen_eng.htm) iv. Human Cloning and Genetic Engineering – (http://www.biofact.com/cloning/) 11. What is biotechnology? [1] Biotechnology is the application of biological principles, organisms and products to perform specific industrial or manufacturing processes. Some economists define it as the use of biological organisms for commercial ends. Biotechnology is not a new technology; brewing of beer, fermentation of wine, and production of cheese is almost as old as human civilization. In brewing, carbohydrates from a variety of agricultural products (rice, wheat, potato, etc) are subjected to fermentation usually by yeast to produce alcohol. Soy sauce has been produced by microbial fermentation of soybean for hundred of years. Since the early 1970’s, biotechnology has received a significant boost from the introduction of a number of powerful new techniques known collectively as genetic engineering. These techniques allow biological scientists to alter the genetic structure of organisms by adding new genes/removing some existing genes that allow the organism to perform new functions. Genetic engineering together with other ways of manipulating and using biological organisms has provided new opportunities with profound implications for a wide range of commercial activities, from agriculture to pharmaceuticals, chemicals, food and industrial to processing, and mining. Reference: Biotech Timeline - (http://www.ncbiotech.org/biotech101/timeline.cfm) Biotech – (http://bioweb.wku.edu/courses/BIOL115/Wyatt/Biotech/Biotech2.htm) Food Biotechnology - http://ific.org/food/biotechnology/index.cfm 8 Trial Version 12. Applications of biotechnology in medicine [3] One type of diabetes (insulin-dependent diabetes) is due to lack of insulin. Insulin acts on certain cells (e.g. muscle cells) in our body to increase the entry of glucose into them and this lowers the level of glucose in the blood. Insulin-dependent diabetes is treated by regular injections of controlled amounts of insulin that serve to bring the insulin levels in the blood to normal. This treatment requires a large quantity of insulin. The demand for insulin is increasing rapidly because of the steady increase in diabetic patients. Until recently, the supply was obtained from the pancreas (an organ that produces insulin) of cows or pigs. This involves tedious isolation procedures. Moreover, if the insulin is contaminated, this could be life threatening. Pharmaceutical companies saw the potential of this large and lucrative market and attempted to produce insulin less costly and more efficiently. Some medical products of genetic engineering Product Application and production source Human insulin Therapy for diabetics; produced by E. coli* Interferon (alpha) Possible treatment for cancer and viral diseases; produced by E. coli Hepatitis B vaccine Prevent hepatitis B; produced by certain yeast that carries a fragment of hepatitis virus gene Taxol Plant product used for treatment for ovarian cancer; produced by E. coli Human growth factor Correct growth defects in children; produced by E. coli Relaxin Ease childbirth; produced by E. coli (*E. coli is used to make most of these products because it is much less harmful and can readily culture in a laboratory.) Biotechnology can also be applied to cure diseases, and the procedure is known as gene therapy. Gene therapy is a biotechnological technique for correcting defective genes with healthy genes. For more information about gene therapy, visit: http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetherapy.shtml#whatis 13. Application of biotechnology in agriculture [3] Development of higher-yield crops, particularly rice and wheat, to satisfy the nutrition needs of people of the less developed countries and to feed an ever-growing world population had been put into action for many decades. The first wave of high-yield crops came about through traditional cross breeding method – using knowledge gained from Mendelian genetics to identify and select strains of crops that exhibit desirable characteristics. However, there are still some disadvantages in the use of high-yield crops. They generally required more fertilizer, more pesticide and herbicide treatments and better irrigation. In short, more costly. Today, biotechnology has been applied to identify, select and create strains that are more resistant to insects and drought and even strains that can produce more nutrients (vitamins). 9 Trial Version Some medical products of genetic engineering Product Application and production source Ice-minus bacteria Lacks normal protein product that initiates undesirable ice formation on plants; produced by P. syringae Insect toxin producing Has toxin-producing gene inserted from B. thuringiensis; bacteria toxin kills root-eating insects that ingest bacteria B. thuringiensis cotton Plans have toxin-producing gene from B. thuringiensis; and corn toxin kills insects that eat plants Pork and beef growth Improve weight gain in pigs and cattle; produced by E. coli hormones Cellulase Enzymes that degrade cellulose (a complex carbohydrate that is very difficult to digest) to make animal feedstocks: produced by E. coli 14. Application of biotechnology in fuel production [3] The availability of energy reserves is getting lower and lower these days. Oil and coal are more and more expensive. Countries without energy reserves have to spend a lot of their national incomes to purchase energy. Some countries are actively exploring ways to find alternative fuels to satisfy the demands, and some turn to biotechnology. One of the success stories is the National Programme in Brazil launched in 1974. In Brazil, the most abundant material was and still is sugar cane. Much of the sugar cane plant is disposed as waste after sugar extraction. These leftovers are fermented to produce alcohol. In 1996, 14.5 billion liters, or about 46 percent of the global total ethanol was produced using this procedure. Some of alcohol produced is used to fuel cars and commercial vehicles. 15. Estimated worldwide biotechnological markets in 2000 [3] Market sector US$ (In millions) Energy 15,392 Foods 11,912 Chemicals 9,936 Health care (pharmaceuticals) 8,544 Agriculture 8,048 Metal recovery 4,304 Pollution control 96 Source: (http://www.accessexcellence.org/RC/AB/IE/Biotech_Industry_Review.html) Some ethnical, social and economical issues in biotechnology As science continues to push the spectrum of biotechnological possibilities further, economic profit for participating sectors and vast improvements in the quality of life for all certainly await. However, before the benefits of applying such technology can be realized, many scholars insist that the ethical, social and environmental consequences of altering the natural genetic code must be thoroughly understood. Some of issues are briefly considered below: 10 Trial Version 16. Positive and negative issues in food biotechnology [2,3] (a) Positive issues With a genetically improved seed, farmers have the ability to reduce expenses, obtain higher crop yields, use less pesticide, produce a more nutritious, better tasting crop, and provide a longer shelf life and better shipping properties. For example, in an era when millions of people starve in third-world countries because they cannot produce enough food to sustain life, biotechnology offers a hope for the future. It has been hypothesized that in the future, modified seeds will allow third-world farmers to continually grow food in areas with poor soil or irrigation by developing crops that more efficiently absorb nutrients, also reducing the need for costly fertilizers. Biotechnology could also help prevent disease and malnutrition in the third-world by producing more healthful crops. As a specific example, a strain of "golden rice" that contains high levels of iron and beta carotene could be available within a few years, holding uncountable benefit for the more than 100 million children who suffer from Vitamin A deficiency. Furthermore, research is already in progress on developing fruits and vegetables that could distribute life-saving vaccines simply through easily distributed, locally grown crops. These are some positive aspects of food biotechnology. (b) Negative issues On the other hand, the general public concerns about human allergic reactions to altered food, the environment and the use of animal genes in plants. Take allergic reaction as an example, the risk of potential allergens (substances causing allergic reactions) in a genetically modified food is of particular concern because of the possibility of transferring a gene that causes allergic reactions to a new food source, without the consumer's knowledge of the transfer. If a gene from a food that commonly causes allergic reactions, like in shellfish or peanuts, is inserted into a food where people would not expect to find such allergens, then the food could potentially harm the consumer. Although regulatory authorities closely monitor its safety, will food on the market with said characteristics be labeled; with the information fully disclosed to consumers? Another common critique of food biotechnology concerns the environmental risks involved in producing genetically altered foods. Would growing of the genetically modified plant harm the surrounding soil, water, animals or other plants? Also, plants and animals with clones genes may grow faster and they may upset the balanced ecosystem and reduce the biodiversity. Lastly, many consumers are concerned about their health when eating new sources of food. Not to mention that some vegetarians “hate” eating genetically modified plants with an animal gene. 11 Trial Version 17. What is gene therapy? [2,3] First discovered in the middle of the 1970’s researchers were able to isolate certain genes from DNA. During the 1980’s the term gene therapy came about and propelled research further. Gene therapy is a technique where the genes causing a defect are themselves substituted by “correct” genes in the patient to cure a disease. At birth, each of us receives a set of chromosomes that contain the genes that code for our personality, appearance, and long term-health. When one of those genes has a mutation or flaw in the DNA structure it can lead to disease. Some diseases related to genetic inheritance are diabetes, sickle cell anemia, and some cancers. With gene therapy we can eliminate these diseases before they even show their first symptom. 18. Positive and negative aspects in gene therapy [2,3] (a) Positive aspects The positive aspect of gene therapy is that it can wipe out genetic disease before they can begin and eliminate suffering for future generations. Gene therapy is also a good technique for diseases not researched yet. All of us carry defected genes and may not know it. Gene therapy is a “medicine” for the future since it can control or eliminate hereditary diseases. In reality, every human carries nearly six defective genes. However, most of us do not suffer any harmful effects from our defective genes because we carry two copies of nearly all genes, one given to us by our mother and the other from our father. Fortunately in most cases, one normal gene is sufficient to avoid all the symptoms of disease. Nonetheless, about one in ten people has, or will develop at some later stage, an inherited genetic disorder, and approximately 2,800 specific conditions are known to be caused by defects (mutations) in just one of the patient’s genes. Some single gene disorders are quite common, for example, cystic fibrosis is found in one out of every 2,500 babies born in the Western World. At present, the method of choice for delivering genes into cells uses the natural ability of viruses to deliver genetic material to cells. (Viruses have evolved a way of encapsulating and delivering their genes to human cells in a pathogenic manner.) Scientists have tried to take advantage of this capability and manipulate the virus genome to remove disease-causing genes and insert therapeutic genes. Currently, gene therapy has only been approved to treat a limited number of diseases, including adenosine deaminase in the US. Nonetheless, despite the low level of approved treatments available today, many attempts are concentrating on applying gene therapy to treat Parkinson’s disease, Huntington’s disease, thalassaemia, sickle cell anemia, leukemia, autism and liver cancer. The future for gene therapy appears bright, as cures for many of the most human diseases stand ready to be discovered. (http://www.duke.edu/web/mms190/biotech/environmental.html) 12 Trial Version Reference: Living with a genetic disorder – (http://www.nature.ca/genome/03/d/10/03d_14_e.cfm) Human Gene Therapy – (http://www.ndsu.nodak.edu/instruct/mcclean/plsc431/students/zhou.html BIO. "Biotechnology in Perspective." Washington, D.C.: Biotechnology Industry Organization, 1990. (b) Negative aspects Despite promising evidence about the benefits of gene therapy, many hurdles must be overcome before applying gene therapy effectively to treat diseases. Some of them are due to procedural and/or methodological difficulties. Short-lived nature of gene therapy Before gene therapy can become a permanent cure for genetic diseases, the inserted DNA in target cells must remain functional and the cells containing the inserted DNA must be long-lived and stable. However, the rapidly dividing nature of many cells prevents gene therapy from achieving any long-term benefits. Immune response Anytime a foreign object is introduced into human tissues, it may stimulate the immune system to generate antibodies to remove them, and this reduces gene therapy effectiveness. Problems with viral vectors Viruses are employed as the carriers in most gene therapy studies, and some potential problems associates with this method are: toxicity, immune and inflammatory responses, and gene control and targeting issues. In addition, there is always the fear that the viral vector, once inside the patient, may recover its ability to cause disease. How can one control the expression? The number of genes incorporated? The amount of protein synthesized? Multigene disorders A number of diseases, such as heart disease, high blood pressure, Alzheimer’s disease, arthritis, cancer, mental illness and diabetes, are caused by the combined effects of variations in many genes. In all these cases, no one gene has the sole yes/no power to say whether a person has a disease or not. It is likely that more than one genetic defect is required before the disease is manifest, and a number of genes may each make a subtle contribution to a person's susceptibility to a disease; genes may also affect how a person reacts to environmental factors. Unraveling these complexed and complicated networks of events will undoubtedly be a challenge for some time to come. 13 Trial Version In conclusion, due to a lack of conclusive evidence proving that genetic treatment has produced therapeutic benefits, the future of gene therapy is still highly skeptical at present. While the scientists made much progress in DNA technologies in food, medicine and energy, perhaps the most important obstacle for further advancement in genetic technology is to overcome its social and ethical implications. Each requires personal thought and reflection to determine one’s opinion. Some ethical and social issues are: 1. Do we understand the risks and limitations of genetic technology? Would you trust the assessment (or testing) of your doctor or a reputable scientist? 2. Where is the line between medical treatment and enhancement? 3. If you had your DNA sequence analyzed by a scientist, who owns and controls your genetic information? Would you agree if he/she supplied it to an insurance company, your (future) employer, or the police? 4. Should genetic testing be performed when no therapeutic treatment is available? 5. Are GM foods and other products safe to humans and the environment? 6. How will these technologies affect developing nations' dependence on the developed countries? 7. In 1997, the European Commission found it difficult to ignore scientific evidence that crops produced through biotechnology are indeed safe. The European Farm Commissioner Franz Fischler approved an application to market gene-modified corn produced in the United States in Europe, but it must fulfill some labeling conditions. Do you think this requirement is reasonable and adequate? For more information, visit http://www.fb.org/views/focus/fo97/fo0106.html. Reference 1. Biotechnology Online - (http://www.biotechnologyonline.gov.au/) 2. Ethical, Legal, and Social issues – (http://www.ornl.gov/sci/techresources/Human_Genome/elsi/elsi.shtml) 3. Gene watch – (http://www.genewatch.org/) 4. Introduction to nucleic acids and application to infectious disease detection (http://www.accessexcellence.org/RC/AB/BA/dnaintro/index.html) 5. Debate over GM products and biotechnology (http://www.ornl.gov/sci/techresources/Human_Genome/publicat/hgn/v12n1/06gmpr oducts.shtml) 6. Gene therapy for cancer: questions and answers (http://cis.nci.nih.gov/fact/7_18.htm) 7. Gene therapy in simple terms – (http://kidshealth.org/parent/system/medical/gene_therapy.html) 8. Scientific issues and social concerns – (http://www.dnapolicy.org/genetics/transfer.jhtml;$sessionid$4I4DCIQAACY4WCQ BAT3RVQQ) 9. Explain “What is a gene?” “Gene therapy” in simple terms – (http://kidshealth.org/kid/talk/qa/what_is_gene.html) 10. Basics on genes and genetic disorders – (http://kidshealth.org/teen/your_body/health_basics/genes_genetic_disorders.html) 11. Molecular Genetics – (http://www.kensbiorefs.com/MolecularGen.html#anchor194140) 12. Using Genomics – (http://www.nature.ca/genome/index_e.cfm) See also the block on “Stem cells and their applications” Animation: 1. Tour of the Basics – (http://gslc.genetics.utah.edu/units/basics/tour/)’ 2. DNA Workshop – (http://www.pbs.org/wgbh/aso/tryit/dna/#) 14 Trial Version Local news [3] Keywords Title 基因影響阿士匹靈藥效 克隆野貓誕 8 小貓 瀕絕種生物有救 遲早樣樣吃不得 海洋細菌基因最少僅千三個 複製風險 水稻基因組序列全圖製成 有助解決饑荒 Newspaper 蘋果日報 文匯報 AM730 東方日報 新報 都市日報 Page number 健康與醫療 A20 國際新聞 A13 港聞 M06 國際 A29 觀點角度 F06 English news digest 46 綠色和平戰船或來港示威 東方日報 港聞 A31 首隻複製狗意義重大 太陽報 社會及專欄 A33 把病毒戴上身 香港經濟日報 專題 C05 基因米疑流入港超市 蘋果日報 港聞 A18 科技展望 50 年: 記憶可下載 水果當藥食 明報 國際新聞 A23 復旦研究基因功能獲重大突破 大公報 中國新聞 A17 轉基因雜草抗除草劑 文匯報 國際新聞 A26 複製豬技術造紅血球生成素 東方日報 國際 A36 無改基因 煮熟不甩色 蘋果日報 國際頭條 A28 有助開發抗衰老產品 港大破解兒童早老症成因 大公報 港聞 A09 世衛:基因食物對人損害不大 東方日報 國際 A10 基因改造番茄抗沙士 蘋果日報 健康與醫療 A19 「有機耕作」農地須生態循環平衡 明報 輕 zone 特區 A20 複製豬心臟 有望移植人體 擁有人類基因年內擬先用 文匯報 國際新聞 A12 猴子作試驗 大豆油幾全屬基因改造 明報 中國社會 B16 吃基因玉米 老鼠腎異變 血液亦異常 專家憂對人類有 文匯報 國際新聞 A12 害 美 75%加工食品含改造成分 明報 國際要聞 A24 港未強制標籤基因食品 明報 國際要聞 A24 英國首次成功複製人類胚胎 成報 國際要聞 A19 改造病毒基因治療天花 蘋果日報 健康與醫療 A20 抗議基因玉米 大公報 科學 B07 轉基因食品 疑慮未息 古法耕種成增產新趨勢 成報 星期綠檔案 A14 稻米混人類基因 引發「人吃人」憂慮 都市日報 國際 P10 日培植人類基因米 被轟科學怪人食物 蘋果日報 國際新聞 A29 港大型米商不進口基因米 明報 輕 zone 特區 A20 綠色和平促標轉基因成份 文匯報 重要新聞 A06 更改基因能改變個人特徵 蘋果日報 國際要聞 A17 基因療法治愛滋大突破 東方日報 兩岸 A09 化石藏細胞軟組織 複製恐龍有望 太陽報 國際新聞 A20 全球基因改造農田增兩成 明報 輕 zone 特區 A23 政府擬訂基因食品標籤指引 太陽報 本地新聞 A32 複製小牛新法 明報 國際 A31 發現沙士異常 RNA 蘋果日報 國際頭條 A25 含人類激素基因牛誕生 星島日報 國際 A20 人類 16 號染色體揭秘 含癌症基因助醫療研究 太陽報 國際新聞 A18 植物基因改造可防禽流 成報 港聞 A08 非基因改造可放心吃 蘋果日報 中國新聞 A28 簡悅威基因斷症之父 《邵逸夫獎》之《基因探索 香港經濟日報 影視樂 C19 者》 Date 2005-08-25 2005-08-23 2005-08-23 2005-08-21 2005-08-14 2005-08-12 2005-08-08 2005-08-06 2005-08-04 2005-08-04 2005-07-27 2005-07-26 2005-07-26 2005-07-24 2005-07-01 2005-06-29 2005-06-24 2005-06-15 2005-06-07 2005-05-24 2005-05-24 2005-05-23 2005-05-23 2005-05-23 2005-05-21 2005-05-19 2005-05-08 2005-04-30 2005-04-26 2005-04-25 2005-04-14 2005-04-09 2005-04-05 2005-03-27 2005-03-26 2005-03-17 2005-03-03 2005-02-18 2004-12-29 2004-12-26 2004-12-25 2004-10-03 2004-09-14 2004-08-28 15 Trial Version Glossary English Autism Autosomal Bacteriophage Biotechnology Chromosomes Denaturation Deoxyribonucleic acid Diabetics DNA Fingerprinting Enzyme Ethanol Fermentation Gene Cloning Gene therapy Genes Genetic Engineering Genetic research Hemophilia Hepatitis B vaccine Herbicide Inflammation Inheritance Mendelian Mutation Nucleic acid Parkinson’s disease Pesticide Replication Ribonucleic acid Sickle cell anemia Slaughterhouses Trait Chinese 孤獨症 常染色體的 噬菌體 生物工程學 染色體 改變本質 去氧核糖核酸(簡稱 DNA) 糖尿病 DNA 指紋術 酵 乙醇,酒精 發酵 基因複製 基因治療 遺傳因子 遺傳工程 基因研究 血友病 B 型肝炎疫苗 除草劑 發炎 遺傳 孟德爾遺傳定律的 變種 核酸 帕金森氏病 殺蟲劑 複製 核醣核酸 鐮狀細胞性貧血 屠殺場 特徵 16