Question

In golden retrievers, the D/d gene codes for an enzyme that produces a pigment. The dominant allele (D) results in a golden pigment, while the recessive allele (d) codes for red pigment.

Additionally, the V/v gene produces a transport protein responsible for depositing the pigment produced by D/d into the hair. When the dominant V allele is present, the color expressed by D/d will be deposited and the dog will be that color (golden or red). However, allele v is recessive and nonfunctional, so in homozygous recessive dogs the pigment is not deposited into the hair, leading to a white or pigment-less dog.

a. For each allele combination below, please list the phenotype and the expected frequency (as a fraction) at which it occurs in the offspring of two heterozygous dogs. (Ex: A_B_ : Green: 9/16)

D_V_

ddV_

D_vv

ddvv

b. What is the overall phenotypic ratio resulting from the cross above? (Ex: 4 black: 6 pink :1 orange)

c. What type of epistasis is this? (Note there is a word bank below)

WORD BANK: Dominant epistasis, Dominant suppression, Complementary gene action, Duplicate gene action, Recessive Epistasis, No Epistasis

Answer 1

Epistasis is a genetic interaction in which one gene suppresses the expression of another gene. The gene which suppresses is called epistatic gene and the gene which is suppressed is called as hypostatic gene.

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