Exam 4 Review & Notes

This is the trnamet the codon an3codon pairing for

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Unformatted text preview: frequently between them. c) They assort independently. d) They are never packaged in the same phage protein coat. e) b and c are correct 20. Two genes that are far apart on a bacterial chromosome are rarely co- transformed because: a) They are rarely contained on the same DNA molecule, and, therefore, rarely enter the same cell. b) Recombina8on occurs too frequently between them. c) They assort independently. d) They are never packaged in the same phage protein coat. e) b and c are correct In co- transforma8on only genes in the same chromosomal region can be transformed; furthermore the closer together the genes lie, the more frequently they will be co- transformed. On the other hand, genes sufficiently far apart wont appear together on a fragment of donor DNA, and will almost never be cotransformed. Transforma8on is an inefficient process, and recipient cells usually take up only a single piece of DNA. 21. Hfr1 transfers genes in the following order: thi- leu- pro- lac with trp transferred very late. An interrupted ma8ng experiment was carried out for the cross Hfr1 (thi+,leu+,pro+,lac+, trp- ) by F- (thi- ,leu- ,pro- ,lac- , trp+). Four sets of recombinants were selected: lac+trp+; pro+trp+; leu+trp+; and thi+trp+. The results for each are plohed below. Which curve represents the leu+trp+ recombinants? 21. Hfr1 transfers genes in the following order: thi- leu- pro- lac with trp transferred very late. An interrupted ma8ng experiment was carried out for the cross Hfr1 (thi+,leu+,pro+,lac+, trp- ) by F- (thi- ,leu- ,pro- ,lac- , trp+). Four sets of recombinants were selected: lac+trp+; pro+trp+; leu+trp+; and thi+trp+. The results for each are plohed below. Which curve represents the leu+trp+ recombinants? Given that all of the recombinants are trp+, it is the thi, leu, pro, and lac which will dictate when they enter the cell. Here we see that leu is second in line, and therefore enters the cell at 20 minutes, aKer thi. 22. A set of T4 rIIA dele8on mutants are presented below. Dashed lines represent deleted sequences. A- E represent segments of the rIIA gene. A point mutant was crossed with each of the dele8on mutants and gave wild type recombinants with mutants # 1, # 3 and #4, but not with mutants #2. Which region does the point muta8on lie in? 22. A set of T4 rIIA dele8on mutants are presented below. Dashed lines represent deleted sequences. A- E represent segments of the rIIA gene. A point mutant was crossed with each of the dele8on mutants and gave wild type recom...
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