1 DNA is generally positively charged due to its nitrogenous bases so an electrical field forces it to move toward a negative pole. The gel causes the molecules to equilibrate at certain locations based on how large they are (and therefore how much charge they have). The gel is porous and allows small fragments of DNA to move more swiftly than larger ones. The phosphate backbone has an overall negative charge, causing it to be attracted to a positive pole. A) I and II B) II and III C) III and IV D) I, II, and III E) I, II, III, and IV 2 lac Z gene? (p. 328)A) When foreign DNA interrupts the lac Z gene, no b -galactosidase can be formed, and X-Gal remains colorless. This allows the researcher to distinguish between recombinant and unrecombinant vectors. B) The lac Z gene is robust: it can be cut and still retain its function of hydrolyzing lactose or X-Gal. C) The lac Z gene naturally has a lot of restriction sites within it, making it easy for cutting and pasting with foreign DNA. D) Only plasmids have the lac Z gene, so it makes obtaining the vector much easier for genetic manipulation. E) The MCS is more stable within an operon than in a region of bacterial DNA which does not encode several tandem reading frames. 3 A) G B) A C) T D) C E) U 4 A) Damage to DNA is hard on the organism, so resistance to drugs and pathogens allow for more survivors of this rough treatment. B) The genes which are removed through in vitro mutagenesis are usually involved in creating antibiotics. This drug resistance allows cells in which these genes are disrupted to still survive. C) The new breeds of organism are of scientific interest only if they have new abilities as compared to the "normal" line from which they were derived. D) Resistance to drugs is a function of being able to modify DNA quickly, so this allows faster formation of knockout lines. E) Knockout lines are easily identified because when exposed to the drug, the nonrecombinant cells all die. 5 A) Vaccines are all safe. B) Because it's a subunit vaccine, the immune system of the person being inoculated is not involved. C) Because of the precision with which transgenic viruses can be constructed, side effects from vaccination are unlikely. D) DNA is not involved in making this vaccine: only proteins from the infectious agent. E) Only a surface protein from the original infectious agent is involved: other genes involved in the infection cycle are carefully excluded. 6 A) that companies would not be able to keep up with the demand for the new variants because they are so popular. B) because we understand so little about how a gene gives rise to a particular protein, we have no idea if introducing new genes into organisms will work or not. C) introgression (horizontal transfer) of genes from agricultural varieties to wild plants would render commercial herbicides ineffective. D) rapid mutation of the genomes of agriculturally important plants could threaten our food supply. E) scientists have no evidence that an introduced gene will behave in any way similar to how it operated in the original organism.
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