The genetic basis of non-disjunction: increased incidence of hyperploidy in oocytes from F1 hybrid mice.

Oocytes from parental mice strains NMRI/Han, C57/bl and Balb/c and from F1 hybrid lines were analysed for aneuploidy due to non-disjunction after gonadotropin-stimulated ovulation. No hyperploid oocytes were present in five of the strains studied. F1 hybrids from crosses of NMRI/HanxC57/bl did ovulate, however, a significantly increased number of hyperploid oocytes, although females from their parental strains show a rather low incidence of non-disjunction. The evidence for a genetic basis for non-disjunction is assessed and possible causative factors are discussed.