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Unformatted text preview: CHAPTER 16 B IOTECHNOLOGY AND G ENOMICS Chapter Outline 16.1 Cloning of a Gene A. Cloning 1. Cloning is the production of identical copies through some asexual means. 2. An underground stem or root sends up new shoots that are clones of the parent plant. 3. Members of a bacterial colony on a petri dish are clones because they all came from division of the same cell. 4. Human identical twins are clones; the original single embryo separate to become two individuals. 5. Gene cloning is production of many identical copies of the same gene. 6. If the inserted gene is replicated and expressed, we can recover the cloned gene or protein product. 7. Cloned genes have many research purposes: determining the base sequence between normal and mutated genes, altering the phenotype, etc. 8. Humans can be treated with gene therapy ; alteration of other organisms forms transgenic organisms. B. Recombinant DNA Technology 1. Recombinant DNA (rDNA) contains DNA from two different sources. 2. To make rDNA, technician selects a vector. 3. A vector is a plasmid or a virus used to transfer foreign genetic material into a cell. 4. A plasmid is a small accessory ring of DNA in the cytoplasm of bacteria. 5. Plasmids were discovered in research on reproduction of intestinal bacteria Escherichia coli. 6. Introduction of foreign DNA into vector DNA to produce rDNA requires two enzymes. a. Restriction enzyme is a bacterial enzyme that stops viral reproduction by cleaving viral DNA. b. The restriction enzyme is used to cut DNA at specific points during production of rDNA. c. It is called a restriction enzyme because it restricts growth of viruses but it acts a molecular scissors to cleave any piece of DNA at a specific site. 7. Restriction enzymes cleave vector (plasmid) and foreign (human) DNA. a. Cleaving DNA makes DNA fragments ending in short single-stranded segments with ¡ sticky ends. ¢ b. The ¡ sticky ends ¢ allow insertion of foreign DNA into vector DNA. 8. The foreign gene is sealed into the vector DNA by DNA ligase . a. Treated cells take up plasmids, and then bacteria and plasmids reproduce. b. Eventually, there are many copies of the plasmid and many copies of the foreign gene. c. When DNA splicing is complete, an rDNA (recombinant DNA) molecule is formed. 9. If the human gene is to express itself in a bacterium, the gene must be accompanied by the regulatory regions unique to bacteria and meet other requirements. a. The gene cannot contain introns because bacteria do not have introns. b. An enzyme called reverse transcriptase can be used to make a DNA copy of mRNA. c. This DNA molecule is called complementary DNA (cDNA) and does not contain introns. d. A laboratory DNA synthesizer can produce small pieces of DNA without introns....
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