Labrador retrievers may be black, brown, or golden in color. Although each color may breed true, many different outcomes occur i
f numerous litters are examined from a variety of matings, where the parents are not necessarily true-breeding. The following results show some of the possibilities. black × brown ? all black
black × brown ? 1/2 black
1/2 brown
black × brown ? 3/4 black
1/4 golden
black × golden ? all black
black × golden ? 4/8 golden
3/8 black
1/8 brown
black × golden ? 2/4 golden
1/4 black
1/4 brown
brown × brown ? 3/4 brown
1/4 golden
black × black ? 9/16 black
4/16 golden
3/16 brown
Part C
Indicate the genotype(s) of dogs that breed true for black color.
Check all that apply.
Check all that apply.
AAbb
AABB
AaBB
aaBB
aaBb
Aabb
AaBb
AABb
aabb
Part D
Indicate the genotype(s) of dogs that breed true for brown color.
Check all that apply.
Check all that apply.
AABb
AaBB
AaBb
AAbb
aaBb
aabb
AABB
Aabb
aaBB
Part E
Indicate the genotype(s) of dogs that breed true for golden color.
This question explains the phenomenon of epistasis. Epistasis encompasses the concept where one gene is dominant in such a way that it completely masks the effect of any other gene present. Here, black is said to be the epistatic gene considering the abundance in its appearance. The ratio of 9:3:4 can be seen in cross 8 which makes this question an example of recessive epistasis. Recessive epistasis occurs when alleles of one locus mask the appearance of alleles, both dominant and recessive, on the other locus. Recessive epistasis is also known as supplementary epistasis.
