The dominant gene of one pair (A) determines the black color, and its recessive allele (a) – the blue color.

The dominant gene of one pair (A) determines the black color, and its recessive allele (a) – the blue color. The dominant gene of the other pair (B) contributes to the manifestation of pigmentation in the organism, its recessive allele (c) does not synthesize pigment. When black individuals were crossed among themselves, individuals with a blue fur color, black and albinos appeared in the offspring. Analyze the genotypes of the parents and the theoretical ratio in the offspring.

A – black color,

a – blue coat color.

B – there is pigmentation,

b – no pigmentation.

An interaction in which one gene affects the expression of another is called epistasis, in this case recessive.

1) Let’s define the genotypes of the parents. Obviously, they are heterozygous for each of the traits, because all color variations are present in the offspring.

2) Crossing scheme:

Parents: AaBb x AaBb,

Gametes: AB, Ab, AB, Ab x AB, Ab, AB, Ab.

With this cross, the split is always approximately 9: 3: 3: 1, but in this case it is 9: 3: 4. 9 individuals will have dominant features (black coat color), 3 – blue, three will have black color in combination with the absence of pigmentation, i.e. albinism, and in 1 case – blue color and lack of pigmentation (albinism).