Relationship between frequencies of univalents and meiotic segregation in different mouse strains and their hybrids.

Although univalents in diakinesis are often used as an estimator for chromosome mis-segregation during meiosis, no clear-cut relationship was demonstrated between both phenomena. In this study, the frequencies of autosomal and gonosomal univalents in diakinesis were related to the frequencies of aneuploid metaphase-II gonocytes during spermatogenesis and oogenesis of different mouse strains and their hybrids (inbred strains: DBA/2J, C57Bl; outbred strain; Swiss, inbred x outbred hybrids: Swiss X C57Bl, C57Bl X Swiss, inbred X inbred hybrids: DBA/2J X C57Bl, C57Bl X DBA/2J). As far as the frequencies of univalents are concerned, they were shown to be strain-dependent and similar in both sexes. Moreover, there is a high non-disjunction rate of DBA males and PMSG-HCG-primed DBA females. Aneuploidy in metaphase II is also strain-dependent but different in both sexes; in the male, a clear decrease of aneuploidy frequencies is observed as compared to the frequency of univalents. This decrease does not occur in females.