Purpose: Diploidy in embryos developing from single pronucleated zygotes can occur following parthenogenetic activation or by asynchronous inflation of pronuclei following fertilization. To distinguish between these two mechanisms, sexing was performed.
Results: The presence of a Y chromosome in the embryo was considered proof that fertilization had occurred. Twenty-one dividing embryos originating from single pronucleated zygotes were analyzed using the polymerase chain reaction or fluorescence in situ hybridization. In total, 43% (9/21) of the embryos showed Y chromosomes.
Conclusion: It can be extrapolated that more than 80% of them originated from fertilized eggs.