[Campbell Biology P.345] In Morgan's cross, why were there no white-eyed females in the F2 g... | Practice Question

In Morgan's cross, why were there no white-eyed females in the F2 generation?

  • A: Because the white-eye allele (w) is lethal in females.
  • B: Because all F2 females inherited a w+ allele from their father.
  • C: Because the Y chromosome carries the dominant red-eye allele.
  • D: Because all F2 females inherited a w+ allele from their mother.

Explanation

To be a white-eyed female, an individual must have the genotype XwXw. This means she must inherit an Xw chromosome from both her mother and her father. In the F2 generation, the father was an F1 male, who had red eyes. His genotype was Xw+Y. Therefore, he could only pass on his Xw+ chromosome to his daughters. Since all F2 females received a dominant w+ allele from their father, none of them could be white-eyed.