Question

Imagine you have just purchased a black stallion of unknown genotype. You mate him to a red mare, and she delivers twin foals, one red and one black. Can you tell from these results how color is inherited, assuming that alternative alleles of a single gene are involved? What crosses could you do to work this out?

Answer 1

Step-by-step explanation:

The results of the twin foals, one red and one black, suggest that the black stallion is heterozygous for the gene-controlling coat color and that the mare is homozygous for the recessive allele.

Assuming that the black coat color is dominant and the red coat color is recessive, we can represent the genotypes of the parents as follows:

Black stallion: Bb (heterozygous)

Red mare: bb (homozygous recessive)

The possible gametes that the black stallion can produce are B and b, while the red mare can only produce b. The Punnett square for the mating of these two horses would be:

| B | b

--|----|----

b | Bb | bb

b | Bb | bb

As we can see, each foal has a 50% chance of inheriting the dominant B allele and being black and a 50% chance of inheriting the recessive b allele and being red. Therefore, the occurrence of one red and one black foal is consistent with the hypothesis that alternative alleles of a single gene determine coat color.

To confirm this hypothesis, we could cross the black stallion to different colored mares. For example, if we mate the black stallion to another red mare and all the offspring are red, this would support the hypothesis that the black stallion is heterozygous for the gene-controlling coat color. Conversely, if we mate the black stallion to a black mare and get a 1:1 ratio of black and red offspring, this would also support the hypothesis that the black stallion is heterozygous for the gene.