In 1910, Morgan did a series of experiments with the fruit fly Drosophila, an organism where females are XX and males are XY. When a mutant male fly with white eyes was crossed with a wild type female with red eyes, none of the F₁ progeny had white eyes but 18% of the F₂ progeny had white eyes. Unexpectedly, all of these white-eyed F₂ flies were males. Based on these results, Morgan concluded that white eyes is caused by a recessive X-linked allele. Suppose Morgan has found that half of the F₁ progeny had white eyes but all of these white-eyed F₁ flies were females. In this case, a valid hypothesis would be

Question

Quizplus · Accepted Answer

If half of the F1 progeny had white eyes and all were females, it suggests that the white eye trait is dominant and linked to the X chromosome. Since females have two X chromosomes, they can express the trait if they inherit one dominant allele.

In 1910, Morgan Did a Series of Experiments with the Fruit