Question

scientist t.h morgan observed that male fruit flies can have white - or red - colored eyes, while female fruit flies rarely have white eyes. he crossed a purebred, white - eyed male fruit fly with a purebred, red - eyed female. all the resultant offspring were red - eyed. he then crossed a red - eyed female and a red - eyed male of the f1 generation. the data of the crosses preformed were recorded in the table

morgan concluded that the gene for white eyes is a recessive trait in male fruit flies. what other conclusion can be drawn from the experiment?

the trait for white eye color in fruit flies is sex - linked

the gene for white eye color is never inherited by the female fruit fly

the trait for white eye color in fruit flies is due to frequent gene mutation

the genes for white and red eye color in male fruit flies are codominant

Explanation:

• In the cross \(F1\) red female \(× F1\) red male, only males show the white - eye phenotype. This indicates that the gene for eye color is located on the sex chromosome (X - chromosome in fruit flies).
• If the gene was autosomal, both males and females would show the white - eye phenotype in a Mendelian ratio. Since only males show the recessive white - eye trait (in the \(F2\) generation of the second cross), it is sex - linked.
• The statement "The gene for white eye color is never inherited by the female fruit fly" is incorrect because females can be carriers (\(X^{R}X^{r}\)).
• There is no evidence in the data about gene mutation causing the white - eye trait.
• Codominance would show a different phenotypic pattern (e.g., both red and white in the same individual in a non - Mendelian way for eye color), which is not observed here.

Answer:

The trait for white eye color in fruit flies is sex - linked.