In horses, the extension gene helps determine coat color. The dominant trait (E) produces black pigment in the coat. The recessive trait (be) produces red pigment. Would a cross between a stallion who is homozygous, (EE), and a mare who is heterozygous (Ee) ever produce a red foal?

Question

A. No, because there would have to be two ressecive alleles
B. Yes, because the amre can pass on her recessive allele
C. No, because they mare cannot pass on her recessive allele
D. Yes, because the stallions dominant allele and the mares recessive allele result in a red coat

Answer 1

The correct answer is A. No, because there would have to be two recessive alleles.

In this scenario, the stallion is homozygous dominant (EE), which means he can only pass on the dominant E allele. The mare is heterozygous (Ee), meaning she can pass on either the dominant E allele or the recessive e allele.

When you cross the stallion (EE) with the mare (Ee), their possible offspring genotypes would be:

• EE (from E from stallion and E from mare)
• Ee (from E from stallion and e from mare)

Since the red coat color (which is determined by the recessive allele e) requires two copies of the recessive allele (ee), and since the stallion can only contribute E alleles, it is impossible for them to produce a foal with the red coat color. Thus, there can never be a red foal from this cross.