A female fruit fly that is heterozygous for the white-eye mutation has red-eyed sons and white-eyed sons in equal proportions:

Question

Quizplus · Accepted Answer

This pattern of inheritance is consistent with X-linked inheritance, where the white-eye mutation is located on the X chromosome. Therefore, the daughters of this female will always inherit one X chromosome from their mother and one X chromosome from their father. However, sons only inherit one X chromosome (from their mother) and one Y chromosome (from their father). Therefore, if the mother is heterozygous for the white-eye mutation, she can pass on either the dominant red-eye allele or the recessive white-eye allele to her sons. If she has an equal likelihood of passing on each allele, then she will have red-eyed and white-eyed sons in equal proportions regardless of the genotype of the male she mates with.

A Female Fruit Fly That Is Heterozygous for the White-Eye