Question

In fruit flies, the allele for white eyes is recessive to the allele for red eyes. In a generation of fruit flies, 45 males with white eyes, 46 females with white eyes, 44 males with red eyes, and 47 females with red eyes are produced. Which of the following is the best conclusion you can make about the parents of this generation?

Answer 1

One parent had white eyes and the other was heterozygous for eye color.

45 males with white eyes, 46 females with white eyes, 44 males with red eyes, and 47 females with red eyes are produced. So the ratio is roughly 1:1:1:1. Eye colour in fruit flies is a sex-linked inheritance.

You can use punnett square to get a clear image on the parent's genotype. Let us analyse the offspring genotypes. Since there is white eye males, the white eye male inherits Y chromosome from the father so it inherits X chromosome with recessive allele from the mother. So the mother has a recessive allele in her genotype. There is also red eye male offspring. It inherit Y chromosome from the father and the X chromosome with dominant allele from the mother. The mother has a dominant allele. Now you can know that the mother is heterozygous and has red eye.

There is white eye female offspring. The offspring must inherit 2 recessive alleles from the parents. One from the mother, the another one must come from the father. The father has the recessive allele and the Y chromosome.

I hope this helps.