Question

the results of thomas hunt morgans last cross are shown in the punnett square below. which of thomas hunt morgans hypotheses was valid based on these results? white eyes are lethal in female drosophila. white eyes are lethal in male drosophila.

Explanation:

In the Punnett square, female flies have genotypes \(X^{R}X^{r}\) (which would have red eyes as \(X^{R}\) is dominant for red eyes). Male flies have \(X^{r}Y\) (white - eyed). There are no female flies with white eyes (which would require \(X^{r}X^{r}\)), but male flies with white eyes (\(X^{r}Y\)) are present. This shows that white - eyed females are not present (if white eyes were not lethal in females, \(X^{r}X^{r}\) would be possible), while white - eyed males (\(X^{r}Y\)) are present.

Answer:

White eyes are lethal in female Drosophila.