A semiselective test for the detection of first- and second-division nondisjunction in Drosophila melanogaster.

Little is known about the relative frequency of induction of nondisjunction in the first and second divisions of meiosis. The killer of prune system is a semiselective Drosophila aneuploidy assay designed to detect chromosome gain resulting from first- or second-division nondisjunction in males. The system can also detect X-Y interchange. Extensive data from nonmutagenized controls indicate that all the expected phenotypes can be recovered. Spontaneous nondisjunction in the first division is three times more frequent than in the second division. Spontaneous interchange between the X chromosome and YS is six times more frequent than between the X chromosome and YL. Exposures of larval males to X-rays, 35 degrees C heat shock, and colchicine were performed. X-ray exposure induced an increase in X-Y interchange events only. A 24-hr heat shock induced an increase in first-division nondisjunction and one type of interchange event. Colchicine failed to induce both nondisjunction and interchange, although it did decrease fertility. The Killer of prune test is of potential value because it allows for the assessment of the relative sensitivities of the two meiotic divisions to perturbations in chromosome number.