Year 12 Human Biology genetics?

Question

Can someone please help??

In Drosophila, yellowish body colour is recessive to normal [grey] body colour. When males from pure-breeding [homozygous] grey bodied stock werre crossed with yellow bodied females, all the female offspring werre rey bodied and all the male offspring where yellow bodied. Suggest an explanation to account for these observations. What further crosses could you make to test your explanation, and what results support it?

Answer 1

The yellow-bodied trait is an x-linked recessive gene. The females have the trait on only one x-gene (out of two) and thus don't show the yellow trait. The males have one X and one Y gene, so all it takes is one yellow gene on their only X-gene for the color to show up.

Ah, high school biology...