Maturation of a binuclear oocyte from the germinal vesicle stage to metaphase II: formation of two polar bodies and two haploid chromosome sets.

We report on a binuclear human oocyte that underwent maturation in vitro from germinal vesicle stage to metaphase II. Following extrusion of two polar bodies, the oocyte was processed for cytogenetic analysis which revealed two separate haploid chromosome sets accompanied by the corresponding polar body chromatin. Tentatively established karyotypes were 23,X and 23,X,ace, respectively. This condition could have resulted in a tripronuclear digynic zygote after monospermic fertilization.