Question

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. female drosophila with white eyes are homozygous recessive. white eyes are the dominant trait in female drosophila.

Explanation:

• In Drosophila, eye - color is a sex - linked trait. The female has two X chromosomes (\(X^{R}X^{r}\) in this case, where \(X^{R}\) is the red - eye allele and \(X^{r}\) is the white - eye allele). A female with white eyes would need to be homozygous recessive (\(X^{r}X^{r}\)).
• The Punnett square shows that there are no females with white eyes in this cross, but if a female had white eyes, she would have to inherit two recessive alleles.
• Option 1: There are no female Drosophila with white eyes in the given cross, but this does not mean white eyes are lethal in females. It just means they didn't inherit two recessive alleles in this particular cross.
• Option 2: There are male Drosophila (\(X^{r}Y\)) with white eyes, so white eyes are not lethal in males.
• Option 4: Since the cross shows red - eye females (\(X^{R}X^{r}\)), white eyes are not the dominant trait.

Answer:

Female Drosophila with white eyes are homozygous recessive.