A. (12 pts.) Suppose that alleles at a certain locus control the tail length of

Question

A. (12 pts.) Suppose that alleles at a certain locus control the tail length of an animal as follows:

                        genotype:                     aa         aA        AA

                        tail length (cm):                       2          3          4

a. Let the frequency of allele A = p, and assume that random mating occurs so that the population is at Hardy-Weinberg equilibrium.   If this is the only locus that affects tail length, and if p = 0.3, then what is the average tail length of animals in this population?

b. Assume that the total phenotypic variance (VP) for this trait is 1.44. If artificial selection is performed by picking animals with an average tail length of 3.7 cm to reproduce, what is the predicted mean tail length in their offspring?

            For bonus credit: would you predict that the heritability of tail length among the offspring would be different than among their parents? If so, describe how it would change.

Explanation / Answer

a. The frequency of allele A = p = 0.3. The frequency of AA genotype is (0.3)2 = 0.09 = 9 individuals out of 100

The frequency of q (a) allele = 1 - 0.3 = 0.7. The frequency of aa genotype (0.7)2 = 0.49 = 49 indivudual out of 100

The frequency of pq (aA) alleles = 2pq = 2 (0.3) (0.7) = 0.42 = 42 out of 100.

The average tail length is

b. Average tail length of selected parents = 3.7 cm

Average tail length of unselected parents = 2.69

S = selection coefficient = Mean of the selected population - mean of the unselected population (or parents)= 3.7 - 2.69 = 1.01

Response to selection R = 1.01 x 1.44 = 1.45

Mean tail length of offspring = unselected mean + predicted response = 2.69 + 1.45 = 4.14 cm

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.