Chromosome Breakage and Sterility in the Mouse

Abstract

SHELL² has shown that the offspring of X–rayed male mice produced before the onset of complete X–ray sterility contain a certain proportion—depending on the dosage—of semi–sterile individuals, which when outcrossed to unrelated animals throw litters of reduced size. This semi–sterility could be shown to be inherited and was assumed to be due to an interchange of segments between non–homologous chromosomes induced by irradiation. The genetical behaviour of semi–sterility was extensively studied in breeding experiments^2,3,1. A great number of valuable data on zygotic lethality during the early embryonic development was also collected by various investigators^4,5,6,10, yet so far no cytological analysis of chromosome behaviour in interchange heterozygotes has been attempted. With this programme in view, three semi–sterile lines, A, B and T, each from a differently treated male, were produced by us using the X–ray technique of Snell.