Developmental profile of glucose phosphate isomerase allozymes in parthenogenetic and tetraploid mouse embryos.

Glucose phosphate isomerase (GPI) allozymes were compared in eggs and embryos of the mouse strains C57BL/6-JHan (GPI-1BB) and 129/Sv (GPI-1AA) under different experimental conditions. The quantitative differences in eggs of the two strains disappeared by the blastocyst stage at day 4 to 5, both in fertilized and diploid parthenogenetic embryos. The degree of degradation of oocyte-coded enzyme molecules and the activation of the embryonic genome for GPI appeared to be equivalent in parthenogenetic embryos from heterozygous females when only one or other maternal allele type remained in the egg after meiosis. Also in tetraploid embryos, generated by electrofusion of homozygous fertilized eggs from the two strains, both genomes seemed to be activated at the same time at day 4; here, however, the GPI-1BB allozyme remained predominant up to day 6.