Testing for nondisjunction in the mouse.

Tests for nondisjunction have been carried out in male and female mice. Ten-day fetal progeny of control and treated adults have been karyotyped to establish spontaneous and induced levels of aneuploidy. In males, the effects of 100 rad x-rays on type A spermatogonia and early primary spermatocytes, and the effects of Mitomycin C (2 mg/kg) on early primary spermatocytes, have been tested. The results show insensitivity of primary spermatocytes to both agents, but a 3.5-fold increase in nondisjunction following spermatogonial irradiation. In females, comparisons have been made between young controls, young x-rayed (5 rad), aged controls and aged x-rayed (5 rad) animals. The "ageing effect" on nondisjunction is observed, but too few fetuses have been analyzed to reach conclusions regarding enhancement of nondisjunction levels by low doses of x-rays.