Question

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

A) The gene involved is on the Y chromosome.
B) The gene involved is on the X chromosome.
C) The gene involved is on an autosome, but only in males.
D) Other male-specific factors influence eye color in flies.

Answer 1

Option B, The gene involved is on the X chromosome.

Step-by-step explanation:

Morgan conducted his studies on Drosophila flies in 1910. He first time noticed a fly with a distinctive white color eye instead of red. Out of curiosity he crossed the white eye fly with a normal red eye fly and noticed that white eyed fly appeared in the second generation and all white eyed flies were male. For the first time, it was observed that some genetic traits are sex linked. In this case the white eye trait was X linked and hence this trait could not appear in female as they have another normal red eye dominant allele which over expressed the white eye allele. However, in male there is no second X chromosome and hence white eyed male possesses recessive white eyed X –chromosome.

Hence, option B is correct

Answer 2

B) The gene involved is on the X chromosome.

Step-by-step explanation:

Thomas Hunt Morgan performed the experiments on the Drosophila and found that genes are located on the chromosomes which are passed o during the reproduction and called it the chromosomal theory of inheritance.

Morgan crossed the white-eyed male mutant to the red-eyed female, a wild trait for eye and observed that during F₁ generation the all-male and female were red-eyed but in F₂ generation only the red-eyed females were produced but all the males were white-eyed.

He found that the gene for the eye colour trait can be linked to the sex of the fly and concluded that it followed the X inheritance pattern as the gene is located on the X chromosome.

Thus, Option-B is the correct answer.