Genetic experiments by Thomas Hunt Morgan and colleagues examined eye color in Drosophila fruit flies. Males are XY and females are XX, and the gene responsible for eye color is on the X chromosome. Red eye color (wild-type) is dominant to white eye color (mutant). The wild type allele is denoted X^w+and the mutant allele isX^w. Which of the statements about eye color in these fruit flies is true?

Question

Quizplus · Accepted Answer

Since the gene responsible for eye color is located on the X chromosome, it is sex-linked. A cross between a red-eyed male (XS1U1P1wY) and a red-eyed female (XS1U1P1wXS1U1P1w) would produce red-eyed males (XS1U1P1wY) and females (XS1U1P1wXS1U1P1w). However, the F1 generation would all be heterozygous females (XS1U1P1wXS1U1P1wY), which when crossed with each other can produce white-eyed males (XS1U1P1wY) in a ratio of 1:1, since the white-eye mutation is recessive and carried on the X chromosome. Therefore, choice D is correct.

Genetic Experiments by Thomas Hunt Morgan and Colleagues Examined Eye