6. Eye color is controlled by two genes. At the BEY-2 gene you can have a domina

Question

6. Eye color is controlled by two genes. At the BEY-2 gene you can have a dominant allele for brown eyes or a recessive alele for blue eyes. At the GEY-2 gene you can have a dominant allele for green eyes or a recessive allele for blue eyes. If someone has both an allele for brown eyes and green eyes, the phenotype will be for brown eyes. Assume that two parents, both who are heterozygous at both the BEY-2 and GEY-2 gene have children. What are all of the potential genotypes and phenotypes of their offspring? (8 points)

Explanation / Answer

BEY-2/BEY-2 or BEY-2/bey-2 = Brown

bey-2/bey-2 = Blue

GEY-2/GEY-2 or GEY-2/gey-2 = Green

gey-2/gey-2 = Blue

For simplicity, assume that

BEY-2 = B

bey-2 = b

GEY-2 = G

gey-2 = g

Parental cross: BbGg X BbGg

Progeny:

B_G_ = 9 = Brown

B_gg = 3 = Brown

bbG_ = 3 = Green

bbgg = 1 = blue

Genotypic ratio = 1:1:1:1:2:2:2:2:4

Phenotypic ratio = 12:3:1

It is an example of dominant epistasis.

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