In cats, the allele that causes curled ears is dominant to the allele that causes normally shaped ears. If two hybrid curled-ear cats are mated, what percentage of the kittens is predicted to have curled ears?

75% (3:4)

Explanation:

A hybrid organism is one that is heterozygous - it carries one curled allele and one normal allele.

Let's use the letter C. The curled allele is C, the normal allele is c.

The heterozygotes are therefore Cc.

The cross between the two cats is Cc x Cc.

                   C             c

C                CC          Cc

c                Cc           cc

Organisms with the genotype CC and Cc are curled ears, since the C allele is dominant to the c allele.

1:4 of the genotypes are CC, and 1:2 are Cc, so 3:4 (75%) have the curled ear phenotype.