Schematic of our strategy for using PB1 chromosomes to produce haploid (A-F) and tetraploid (A’-F’) parthenogenetic embryos.

A: Removal of nuclear materials from PB1 and MII oocytes. B: Enucleated MII oocyte. C: Injection of PB1 chromosomes into an enucleated MII oocyte. D: Electrical stimulation. E: Segregation of sister chromatids. F: The polar body is extruded and the embryo becomes haploid. A’: Removal of the first polar body from an MII oocyte. B’: MII oocyte with nuclear materials and without PB1. C’: PB1 chromosomes are injected into the intact MII oocyte. D’: Electrical stimulation. E’: Culture of the reconstructed oocytes with cytochalasin B (3 h, to inhibit polar body ejection). F’: The tetraploid embryo.