Second and sex chromosome nondisjunction is increased compared to wild type in homozygous males (but not in females). Nondisjunction occurs at the first meiotic division. Homozygous (but not heterozygous) males produce an excess of X and nullo-XY sperm as compared to Y and XY sperm. The frequency of 2nd chromosome nondisjunctions is dependent, in part, on the Y chromosome present in the genome. The differences are attributable to variable recoveries of nullo-2 but not diplo-2 offspring. There is a high correlation of nondisjunction for the 2nd and sex chromosomes. Nearly half of the 2nd chromosome exceptions are also nondisjunctional for the sex chromosomes. Among the double exceptions there is an excess of XY nullo-2 and nullo-XY diplo-2 gametes.