Practice For Exam #1
We were given a worksheet to work on in class, and then we took up the answers by having a
student go up to the board writing down his/her process in getting his/her answers.
1. A farmer bought a herd of 600 sheep, taken from a freely breeding population, and later
found that 50 of the animals had an economically undesirable feature, crinkly-hair,
caused by the recessive allele cr. Assuming Hardy-Weinberg proportions,
a. What is the frequency of this undesirable allele in the herd?
Let cr represent crinkly hair
Let CR represent non-crinkly hair
q = 150/600
q = 0.25
q = 0.5
b. What proportion of the herd is likely to be heterozygous?
p = 1 – w
p = 1 – 0.5
p = 0.5
p(CRcr) = 2pq
p(CRcr) = 2(0.5)(0.5)
p(CRcr) = 0.50
c. The owner than separates all those animals showing crinkly-hair and sends them
for slaughter. He allows the remaining animals to breed freely. What proportion
of the next generation of lambs would be expected to show crinkly hair?
Therefore, 600 x 0.50 = 300 sheep will most likely be heterozygous (2pq)
p = 600 *0.25 = 150 homozygous sheep (for non-crinkly hair)
q = ?
p = 150/ 450 = 0.33
p = 0.57, q = 0.43 q = 0.19
2. Suppose genotypes AA, Aa, and aa have frequencies in zygotes of 0.16, 0.48, and 0.36,
respectively, and relative fitnes