INCREASED INCIDENCE OF UNPARTNERED SINGLE CHROMATIDS IN METAPHASE-II OOCYTES IN 39,X(XO) MICE

Since rare cases of sex chromosome anomalies such as XXX and XXY were observed in the offspring of our XO breeder mice, we performed a cytog enetic analysis of metaphase II oocytes of XO mice to determine whethe r any changes in chromosomal configurations occur. We found a signific antly increased incidence of unpartnered single chromatids in metaphas e II oocytes of XO mice. Such single chromatids may contribute to embr yonic aneuploidy. In addition, the tendency of the X-chromosome to seg regate non-randomly to the oocyte rather than to the polar body was co nfirmed.