Question

In fruit flies, red eyes (R) are dominant over white eyes. The results of a cross between two fruit flies creates the following offspring:

Red eyes = 264
White eyes = 270
What are the most likely genotypes of the
parents? Use a P-square to prove your answer.

Answer 1

one parent is heterozygous and the other parent is homozygous recessive

Step-by-step explanation:

Since red eyes are the dominant trait, both parents must carry the recessive gene for white eyes in order to have offspring with white eyes. However, if both parents were only heterozygous (one gene for each eye color), then the ratio of offspring with red eyes to white would be 3:1. There are more offspring with white eyes than red eyes present, so on parent must be homozygous recessive (have both genes for white eyes).