AP Biology genetics question?

Question

In Andalusian fowl, F^B is the gene for black plumage. F^b is the gene for white plumage. These genes show incomplete dominance. The heterozygous condition results in blue plumage. List the genotypic and phenotypic ratios expected from the crosses:

a) black X blue

b) blue X blue

c) blue X white

Answer 1

Hi Tzuyu,

"Incomplete dominance" happens when the presence of a dominant allele does not completely hide the presence of the recessive allele, as one would expect. Here, the heterozygote, which would have a genotype of F^BF^b, resulting in blue feathers. A homozygous dominant fowl would be F^BF^B, and a homozygous recessive fowl is F^bF^b.

A) Black x Blue = F^BF^B x F^BF^b

Offspring Genotypes: 2 F^BF^B, 2 F^BF^b

Offspring Phenotypes: 2 Black, 2 Blue

B) Blue x Blue = F^BF^b x F^BF^b

Offspring Genotypes: 1 F^BF^B, 2 F^BF^b, 1 F^bF^b

Offspring Phenotypes: 1 Black, 2 Blue, 1 White

C) White x Blue = F^bF^b x F^BF^b

Offspring Genotypes: 2 F^bF^b, 2 F^BF^b

Offspring Phenotypes: 2 White, 2 Blue