Quiz #3 answers

Correct answers in bold

  1. (5 points) The figure to the right shows a chromosome during mitotic metaphase. Which term best describes the structure of this chromosome? (Note: see bottom left panel of textbook Figure 5.5 for image)

a) metacentric

b) acrocentric

c) chiasma

d) compensatory


2. (5 points) The Y chromosome in humans is thought to have evolved from a homologous partner to which other chromosome?

a) Chromosome 21

b) Chromosome 22

c) The Z Chromosome

d) The X Chromosome


3. You are studying the rb gene (rb indicates recessive mutant allele, + indicates wild-type) and cv gene (cv indicates recessive mutant allele, + indicates wild-type) in Drosophila. Both genes are on the X chromosome. You set up a testcross between a doubly heterozygous female and a male tester fly. You infer the following genotypes from the phenotypes observed in the male progeny of this cross:


Genotype                                Number Observed

+   + / Y                                              90

+ cv / Y                                              11

rb + / Y                                             9

rb cv / Y                                             90


Part A (5 points): Does this data suggest that the rb and cv genes are linked?

a) Yes

b) No

c) Not Enough Information Provided


Part B (5 points): What is the genetic distance (in cM) between rb and cv?

(9+11)/200 = 20/200 = 0.10 recombination freq. (x100) = 10 cM

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