Question

Calvin Bridges determined that the rare white-eyed males produced from the mating of true-breeding red-eyed females with white-eyed males resulted from a nondisjunction of X chromosomes in the female parent during meiosis. If such a mating produced 1234 red-eyed progeny and three white-eyed males, what is the observed rate of nondisjunction of the X chromosomes?

Answer 1

In an X-linked cross between a white-eyed male and a female heterozygous for red eye color, the ratio of offspring will be 1:1 for red-eyed females to white-eyed males.

Step-by-step explanation:

In Drosophila fruit flies, the gene for red eyes, which is located on the X chromosome, is dominant over the gene for white eyes. The genotype of a white-eyed male is XwY, while the genotype of a female that is heterozygous for red eye color is XWXw. When these two flies are crossed, the offspring will have a ratio of 1:1 for red-eyed females (XWXw) to white-eyed males (XwY).