Question

the gene for body color and wing shape reside on the same chromosome in fruit flies. after crossing female flies having gray bodies and normal wings with male flies having black bodies and vestigial wings, morgan observed that some of the f₁ flies had nonparental phenotypes (gray bodies with vestigial wings, or black bodies with normal wings). what accounts for this? some flies with those phenotypes accidentally contaminated the cross. a certain percentage of the f₁ generation was affected by genetic mutations. the alleles for wing shape and body color recombined by crossing over. the alleles underwent independent assortment during meiosis.

Explanation:

When genes are on the same chromosome (linked genes), non - parental phenotypes in offspring can occur due to crossing over during meiosis. Crossing over is the exchange of genetic material between homologous chromosomes, which can lead to new combinations of alleles. Independent assortment applies to unlinked genes on different chromosomes. Mutations are rare and not the most likely explanation here, and contamination is an unlikely reason for the observed non - parental phenotypes.

Answer:

The alleles for wing shape and body color recombined by crossing over.