Question

A homozyguos curved-horned stallion is crossed with a spiral-horned mare.

What is the mare’s genotype (with respect to her horn)?

What proportion of the offspring will have a heterozygous genotype? (Percentage)
What proportion of the offspring will have a homozygous genotype? (Percentage )
What proportion of the offspring will have a curved horn phenotype?
What proportion of the offspring will have a spiral horn phenotype?

Answer 1

Let us assume that the genotype for curved horns is C (dominant) and spiral horns is c (recessive).

Finding the mare's genotype,

Parents: CC x cc

F1 Generation (Mare): Cc, Cc, Cc, Cc (After meiosis.)

It can be seen that all the 4 mares in the F1 generation are hybrid (heterozygous) with curved horns, since the recessive gene doesn't express itself because of the heterozygous genotypes.

Since all four offspring have a heterozygous genotype, proportion of the offspring having a heterozygous genotype = 4/4 = 100%.

Since none of the offspring have a homozygous genotype, proportion = 0/4 = 0%.

Proportion of the offspring that will have a curved horn phenotype = 4/4 = 100%

Proportion of the offspring that will have a spiral horn phenotype = 0/4 = 0%.

Hope this helps ya.