A whiteeyed male fly is mated to a homozygous redeyed female

A white-eyed male fly is mated to a homozygous red-eyed female. Sons and daughters are mated. What phenotypic ratios do you expect in in the \"grandchildren\"?

Solution

ANS: B. Females: 100% red-eyed, Males: 50% red-eyed, 50% white-eyed

Explanation:

Morgan deduced that gene with white eyed mutation is on X chromosome is a sex linked gene.

Sex-linked inheritance refers to transmission of traits on sex chromosomes.

Females (XX) may had two red eyed alleles and had red eyed color.

The males had only a single allele and it will be red eyed if they had red-eyed allele or white-eyed if they have a white eyed allele.

If the white-eyed male fly is mated to a homozygous red-eyed female, producing many F1, all with red eyes. In F2 generation of grand children are 75% with red eyed and 25 % are with white eyed. But it is not normal 3:1, only the males have white eyes.

Morgan produced 1237 F1 flies, all with red eyes.

Morgan produced F2 flies are,

     2459 Red- eyed females,

     1011 Red- eyed Males,

      782 White- eyed Males.