Aneuploidy in mouse fetuses after paternal exposure to x rays

ANEUPLOIDY can result either from non-disjunction, giving trisomy and monosomy, or from chromosome damage leading to loss of chromosomes (monosomy) only. It is known that chromosome loss can be induced after irradiating post-meiotic male germ cells1, but apart from findings on radiation-induced non-disjunction in oocytes from mice2–5, there is no evidence that paternal exposure to X rays induces chromosomal mal-segregation during male meiosis to produce monosomic and trisomic offspring. Szemere and Chandley6 did observe significantly more mal-segregated X and Y chromosomes in spermatocytes II after 100 and 200 rad had been given during preleptotene and pachytene, but failed to recover aneuploid fetuses in progeny from irradiated males. They suggested that only a few aneuploid spermatocytes would be transmitted to the next generation. We have now shown that such induced aneuploidy is indeed transmitted and can be detected in a monosomic and trisomic condition in F1 fetuses on day 9.5 of gestation.