In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only.
-Two heterozygous birds are mated. What fraction of the male offspring is expected to exhibit cock feathering?
A) 0
B) 1/8
C) 1/4
D) 1/2
E) 3/4

Question

In domestic chickens, some males display a plumage pattern called cock feathering. Other males and all females display a pattern called hen feathering. Cock feathering is an autosomal recessive trait that is exhibited in males only. 
-Two heterozygous birds are mated. What fraction of the male offspring is expected to exhibit cock feathering?
A) 0
B) 1/8
C) 1/4
D) 1/2
E) 3/4

Quizplus · Accepted Answer

Cock feathering is an autosomal recessive trait, meaning that it is carried on one of the non-sex chromosomes and that two copies of the recessive allele are required for the trait to be expressed. In males, the presence of even one dominant allele will result in hen feathering. In females, the presence of two recessive alleles is required for cock feathering to be expressed.In this case, both parents are heterozygous for the cock feathering trait, meaning that they each carry one dominant allele and one recessive allele. When these two birds are mated, the possible offspring genotypes are:- 1/4 homozygous dominant (HH) - hen feathering- 1/2 heterozygous (Hh) - hen feathering- 1/4 homozygous recessive (hh) - cock featheringTherefore, the fraction of male offspring that is expected to exhibit cock feathering is 1/4.

In Domestic Chickens, Some Males Display a Plumage Pattern Called