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You are setting up a cross between two D. melanogaster fruit flies. The female flies (XX) are entirely wild-type. The male flies (XY) have a visual phenotype which makes their eyes white, instead of the usual WT (wild-type) reddish color.

After crossing, you observe the F1 generation. All of the F1 flies, both male and female, are phenotypically WT.

You allow the F1 males to mate with the F1 females and observe the progeny. The results are as follows:

All of the F2 females are phenotypically WT.

The males display three distinct phenotypes. The largest subset of flies is phenotypically wild-type. The next largest subset of flies has white eyes as seen in the original parental males. The last set of flies, a subset which is only slightly smaller than the white-eyed flies, have brown eyes. These proportions occur in a roughly 9:4:3 ratio.

Based on the flies you see in the F1 generation, you can conclude that the allele that results in white eyes is
Select Option co-dominant dominantincompletely dominantrecessive
. Based on what you see in all of the flies in the F2 generation, you can conclude that the allele causing white eyes is
Select Option autosomalmitochondrialX-linked
. Based on what you see in the male flies in the F2 generation, the number of mutant genes involved in this cross is most likely
Select Option onetwothree
. In the F2, we see three colors. The most likely explanation for this result is
Select Option co-dominanceincomplete dominancerecessive epistasisdominant epistasis
.
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