9.28) The presence of horns in some breeds of sheep is governed by a sex- influe
ID: 166513 • Letter: 9
Question
9.28) The presence of horns in some breeds of sheep is governed by a sex- influenced gene that is dominant in males and recessive in females. if a sample of 300 is found to contain 75 horned individual, (a) what percentage of the females is expected to heterozygous, and (b) what percentage of the males is expected to be horned? Show your work for both parts. NOTE: The back of the book says the answers are: A). 50% B). 75% , I would like to know how they came up with these answers showing work, thank you!
Explanation / Answer
Answer:
The frequency of horned phenotype (q^2) = 75/300 = 0.25
The frequency of horned allele (q) = Sqrt 0.25 = 0.5
The frequency of hornless allele (p) = 0.5 (as p+q=1)
a). The frequency of heterozygous in females (2pq) = 2 * 0.5 * 0.5 = 0.5
The percentage of the females is expected to heterozygous = 0.5 = 50%
b).
Both homozygous and heterozygous horned genotypes are horned in males as the trait is dominant in males. It comprises 75%
So, the percentage of the males is expected to be horned = 75%
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