7. The mutation for cataracts (c) occurs on a gene represented by the letter E. Owls that are homozygous for the mutation (EcEc) exhibit cataracts. Owls that are homozygous for normal eyes are EE and owls that are carriers of the mutation but do not exhibit cataracts are EEc.

What percentage of the offspring in a cross between parents with the genotypes EE and EcEc will exhibit cataracts?

A. 0%
B. 25%
C. 50%
D. 75%

To determine the percentage of offspring that will exhibit cataracts in a cross between parents with the genotypes EE and EcEc, we need to understand how the genes are inherited and how they interact.

In this case, the mutation for cataracts (c) occurs on the gene represented by the letter E. Owls that are homozygous for the mutation (EcEc) exhibit cataracts, while owls that are homozygous for normal eyes are EE, and owls that are carriers of the mutation but do not exhibit cataracts are EEc.

When two parents with genotypes EE and EcEc are crossed, their possible offspring genotypes are:

1. E from the EE parent and c from the EcEc parent:
- Genotype: Ec
- Phenotype: They are carriers, but do not exhibit cataracts.

2. E from the EE parent and E from the EcEc parent:
- Genotype: EE
- Phenotype: They are homozygous for normal eyes, so they do not exhibit cataracts.

Therefore, none of the possible offspring in this cross will exhibit cataracts, resulting in:

Answer: A. 0%

50%