If a female and male offspring from a specific cross in fruit flies are allowed to mate, what is the expected ratio of their offspring?

The expected ratio of offspring from a cross between a female and male fruit fly can be understood through Mendelian genetics, particularly when considering the genes responsible for eye color in Drosophila melanogaster. In this scenario, assume that the red eye color is dominant over white eye color.

When a red-eyed female is crossed with a red-eyed male, and if we consider that the red-eyed female can be either homozygous dominant or heterozygous for the eye color trait, the resulting offspring ratio will depend on the genotype of the parents.

If both parents are heterozygous (for example, Rr for red eyes, where R is the dominant allele and r is the recessive allele for white eyes), the classic Punnett square yields the following ratios for the offspring:

• 1 RR (homozygous red-eyed)

• 2 Rr (heterozygous red-eyed)

• 1 rr (homozygous white-eyed)

Since female fruit flies have two X chromosomes and males have one X and one Y chromosome, it can be deduced that females will have a chance of being either red-eyed or white-eyed, while males will have a direct correlation to their X chromosome from the mother. Thus