Genetic Variation in the Timing of First Cleavage in Mice: Effect of Paternal Genotype

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Abstract
The effect of the Y chromosome of BALB/cWt on the timing of cleavage was investigated because of its effects on the occurrence of hermaphroditism and alterations in sex ratio. Eggs from SJL .times. SWR F1 mice (SFF1) that had been fertilized in vivo were cultured in vitro in defined medium. The mean time of 1st cleavage depended on the strain of male parent. Cleavage occurred in eggs fertilized by BALB/cWt males 4 h later than in eggs fertilized by SFF1 males. Eggs fertilized by SJL or SWR males cleaved at different times, but in both cases later than those fertilized by the F1 hybrids. Measurements on eggs fertilized by males from a pair of stocks consomic for the BALB/cWt or SJL Y chromosomes showed that the genetic determinants of the significantly earlier cleavage caused by SJL males were autosomal rather than Y-linked, and were unrelated to those involved in the production of hermaphrodites. No differences were found between BALB/cBy, C57BL/6By and their recombinant inbred derivative CXBH in their effects on the timing of 1st cleavage. Eggs, from SFF1 females, that had completed 1st cleavage were more likely to form blastocysts when the male was an SSF1 rather than a BALB/cWt mouse.