Quiz #5 Answers

Correct answers in Bold.

#1. (5 points) When population size is large and mutation rates are low (~10-8), as an evolutionary force mutation is generally characterized as:

A. Strong

B. Weak

C. Balancing

D. Beneficial


#2. (5 points) You sequenced a RNA polymerase gene from Caenorhabditis elegans, and a RNA polymerase gene from its sister species Caenorhabditis briggsae. You performed a Ka/Ks analysis on these genes and the calculated value was 0.005. What kind of selection is mostly likely influencing the evolution of these genes?

A. Negative (or, purifying) selection

B. Positive (or, directional) selection

C. Balancing selection

D. Neutrality (no selection)


#3. You are studying the population genetics of Mendel’s pea plants. You remember that they are diploid, and that the G allele is fully dominant and results in yellow peas; the g allele is recessive and results in green peas (when homozygous, of course). Upon visiting a field, you discover 200 pea plants. 160 of the plants produce yellow peas, and 40 of the plants produce green peas. Assume this population is in Hardy-Weinberg equilibrium.


Part A. (3 points) What is the genotype frequency for gg plants?

40/200 = 0.20


Part B. (3 points) What is the allele frequency for g?

q = 0.447


Part C. (4 points) What is the expected number of heterozygous plants in this population?

98.9 (or round to 99) plants

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