Midterm Key

Midterm Key - Biol 432L Midterm Oct 6, 2008 Name: 1 Midterm...

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Biol 432L Midterm Oct 6, 2008 Name: 1 Midterm 1, Answer Key Oct. 26, 2009 Honor Pledge : I have neither given nor received any unauthorized help on this exam: Name Printed : ______________________________________________________ Signature :__________________________________________________________ 1a. (2 pts) Imagine you have two pure breeding plants of the same species. One has round leaves, red flowers and hairy stems and the other has long thin leaves, purple flowers and hairy stems. If you cross them, the F1 has long thin leaves, purple flowers and hairy stems. Which allele is dominant for leaf shape? Thin Which allele is dominant for flower color Purple 1b. (2 pts) You cross 2 F1s and get the following numbers of progeny. How many loci with different segregating alleles can be measured. Two 18 thin, purple, hairy, 6 thin, red, hairy, 6 round, purple, hairy: 2 round, red, hairy Are the loci linked or segregating independently? Unlinked 2a. (1 pt) What physical structure is required for transfer of the F plasmid between E. coli bacteria?. Where are the genes for that structure located, plasmid or chromosome? The pilus. On the F plasmid 2b. (2 pts) Why did we have to include a streptomycin resistance gene in the recipient strain in our Hfr conjugation experiment? The donor had wild type alleles for the genes that were auxotrophic in the recipient but could not grow on Streptomycin. Only recombinants could 2c . (2 pts) Hfr strains of E. coli have an F plasmid integrated into the bacterial chromosome. The F plasmid replicates with the bacterial chromosome instead of
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Biol 432L Midterm Oct 6, 2008 Name: 2 replicating on its own, separate from the chromosome. Because of the integrated F plasmid, Hfr strains are capable of mating with F- E. coli. What sequences on the F plasmid allow it to become integrated into the bacterial chromosome? Insertion sequences or transposable elements common between the plasmid and the bacterial chromosome. 3. In the paper we discussed in the lecture, Lederberg and Tatum demonstrated that E. coli can exchange genetic information. a. (2 pts) How did Lederberg prove that he found genetic recombination between strains and not simply back mutation. It took two separate experiments. He measured the reverse mutation frequency for one trait. He then used
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Midterm Key - Biol 432L Midterm Oct 6, 2008 Name: 1 Midterm...

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