Question

Grandma and Grandpa Smiley are heterozygous for the star eye shape. If one of their heterozygous children married a girl with blast-type eyes, what percentage of their grandchildren should have starry eyes? What percent would have blast-type eyes?

Answer 1

50%

Step-by-step explanation:

Grandma and Grandpa are both heterozygous for starry eyes. Lets say the starry eyes allele is S, and blast allele is s. Grandma and grandpa are both heterozygous, so Ss.

Their daughter is also heterozygous, so must be Ss. They had children with a woman with blast type eyes, which must have the genotype ss.

To work this out, we draw up a Ss x ss punnet square (attached)

The possible genotypes are Ss (50%) and ss (50%). So there is a 50% chance their child would have blast eyes (ss).