Question

Albinism in most animals is an epistatic trait characterized by a lack of melanin pigment in the eyes, skin, and hair. If the allele for albinism is a, the allele for brown coat color is B, and the allele for red coat color is b, which of the following genotypes would result in an albino cow

a. Albino- aaBB, aaBb, aabb
b. Brown- A-BB, A-Bb
c. Red- A-bb

Answer 1

a. Albino- aaBB, aaBb, aabb

Step-by-step explanation:

In epistasis or epistatic gene interaction, an allele or a pair of alleles in one locus modifies the expression of an allele or a pair of alleles in another locus.

Epistatic gene interactions are of different types:

• Dominant epistasis: involves a dominant allele on one locus masking the expression of both dominant and recessive alleles at another locus.

• Recessive epistasis: involves a recessive allele on one locus masking the expression of both dominant and recessive alleles at another locus.

• Dominant inhibitory epistasis: When a gene on one locus suppresses the expression of a gene on another locus.

• Duplicate dominant/recessive: involves a dominant/recessive allele masking the expression of recessive/dominant alleles at two loci.

• Polymeric gene interaction: two dominant alleles combine together resulting in an intensified phenotype.

In this case, the presence of albinism allele a on one locus modifies the expression of alleles B and b on separate loci.

Hence, aaBB, aaBb, and aabb will always result in albinism.

The correct option is a.

Answer 2

Option A aaBB, aaBb, aabb

Step-by-step explanation:

Since this condition is an epistaic trait, thus if the trait is inherited in the homozygous recessive pattern, the condition, no matter how dominant the other traits (brown coat and red) are become expressed. Thus, an albino cow would be produced with the genotypes: aaBB, aaBb, aabb.