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AP BIOLOGY: Chapter Nineteen Review Answers 
1. Nucleotides at the ends of recognition sequences are complementary. Although the DNA molecule is cut across both strands, the ends are single-stranded and complementary ("sticky"): often able to bind to other segments of DNA. 2. A chimeric genome is artificially made and consists of DNA from distinctly different organisms. A vector is a genome used specifically to insert foreign DNA into a host cell. Each of the host cells (usually, but not exclusively, bacteria) that have foreign DNA in them are replicated separately. These individual transformed host cells represent a clone library. 3. Clones that do not contain vectors can be identified by exposing the clones to something from which the vectors confer some sort of protection, such as antibiotic resistance. If the clone doesn't have the resistant vector, it will die when exposed to the antibiotic. To remove clones with vectors missing the desired piece of DNA, indicators such as X-gal can be used, which turns blue when metabolized by a cell. If the cell is missing the enzymatic machinery to metabolize X-gal, it won't turn blue and is readily identified. 4. The probe in a Southern Blot is a strand of nucleic acid that has been irradiated (usually with 32P). The radioactive nucleic acid hybridizes with the desired genetic fragment in the blot, which is subsequently identified by its radioactivity. 5. Transposons serve to make any given fragment of DNA isolated by restriction endonucleases almost certainly unique to the individual. By creating these fragments and looking at the differences in them among individuals (polymorphisms) using gel electrophoresis and radioactive probing, the identity of an individual can almost certainly be ascertained-very useful when any DNA is available from an "unknown assailant" in the form of sperm or blood cells with which DNA from suspects can be compared. 6. DNA fragments are dissociated into single strands by heat. The enzyme used to replicate the single strands of DNA is a heat-stable DNA polymerase from a hot springs bacterium. The DNA was originally dissociated in the presence of an excess amount of oligonucleotide, which functions not only in keeping the DNA from reannealing, but as a primer for the new DNA synthesis. 7. A harmless virus (such as cowpox) is recombined with a pathogenic one (such as herpes). Upon introduction of the recombinant vaccine into an animal, the animal develops an immune response to the pathogenic virus (as well as the harmless one). Only a small part of the genome of the pathogenic virus is used, enough to mount an immune response, but not enough to trigger development of the disease. 8. The Ti plasmid is most commonly used, typically affecting broadleaf plants such as tomato, tobacco, and soybean. Using this technique, scientists have been able to confer herbicide, virus, and insect resistance into plants, greatly improving crop yields. 9. BST is a synthetic growth hormone administered to cows to increase milk production. It is a hormone that cows already manufacture normally, and has no effect on consumers of milk (or any other part of the cow!). 10. Bacteria are used that not only are not dangerous to living organisms, but are usually manufactured so that they are incapable of living outside of the laboratory. | ||||||||||||
The information contained on the chapter guide pages has been obtained from the publisher's website. They are merely reproduced here for easier access. Please contact Asim Ali if you have any questions or comments.
