Question

A single gene mutation in cats can result in curly ears (see image). The cats are healthy and normal beyond the ear structure, which actually changes after birth.
This trait is recessive, and the allele for curly ears is $ and the allele for regular ears is S.

Which of the following responses are true? (SELECT ALL correct answers)
curly_ear_cat.jpeg

a. A cross between this cat and another curly ear cat will result in 100% curly ears
b. A cross between this cat and another curly ear cat will result in 50% straight ears
c. The genotype of the cat in the picture is $$
d. The phenotype of the cat is $$
e. Mutations are always bad, even in cats.
f. A cross between this cat and another curly ear cat will result in 100% straight ears
g. The genotype of the cat in the picture is S$
h. A cross between this cat and a homozygous normal ear cat will result in 100% normal ears

Answer 1

The following responses are true;

a. A cross between this cat and another curly ear cat will result in 100% curly ears

c. The genotype of the cat in the picture is $$

g. The genotype of the cat in the picture is S$

h. A cross between this cat and a homozygous normal ear cat will result in 100% normal ears

Explanation:

Because the allele for curly ears is recessive, then all the cats with curly ears have a homozygous recessive genotype ($$) because the don't have a domiant allele (S) to mask the effect of the recessive allele.

A cross between two curly-eared cats (which means they both are homozygous recessive individuals) will result in 100% curly-eared offspring with homozygous recessive genotypes.

A cross with homozygous dominant individual will result in all offspring being straight-eared but with heterozygous genotypes.