Figure 1.

X chromosome nondisjunction leads to aberrant inheritance of sex-linked traits. (A) Proper chromosome segregation of X chromosomes in females results in wild-type XX females and vermilion-eyed XY males. (B) Nondisjunction of X chromosomes at the first meiotic division produces diplo-X and nullo-X eggs containing two and zero X chromosomes, respectively. Fertilization of these nondisjunctional eggs results in the production of exceptional red-eyed sterile X0 males and exceptional vermilion-eyed XXY females (adapted from Bridges 1916).