Question

Normal fruit flies have brownish-yellow bodies, and this body color is dominant. A mutation in the gene for body color can produce flies with an ebony body color. A homozygous normal fruit fly (e+e+) is crossed with a homozygous ebony fruit fly (ee). What is the predicted outcome of this genetic cross?

Answer 1

In this genetic cross, the homozygous normal fruit fly (e+e+) is crossed with a homozygous ebony fruit fly (ee). The body color gene has two alleles, e+ for the normal brownish-yellow body color (dominant) and e for the ebony body color (recessive).

The genotype of the normal fruit fly is e+e+ (homozygous for the normal allele), and the genotype of the ebony fruit fly is ee (homozygous for the ebony allele).

When these two flies are crossed, their offspring will receive one allele from each parent. The possible combinations are as follows:

Offspring genotype:
- e+e+ (normal brownish-yellow body color)
- e+e (normal brownish-yellow body color)
- ee (ebony body color)

Since the homozygous normal fruit fly (e+e+) is crossed with a homozygous ebony fruit fly (ee), all of the offspring will receive one ebony allele (e) from the ebony fruit fly parent. Therefore, all the offspring will have an ebony body color, resulting in a phenotypic ratio of 100% ebony flies.