Three paternally imprinted regions are sequentially required in prenatal and postnatal mouse development

Reproduction in mammals is primarily through fertilization of the oocytes and sperms generated by the females and males,respectively.Fusion of two haploid genomes leads to formation of the diploid zygotes,which sequentially gives rise to the pre-implantation and post-implantation embryos before live pups are bom.Although asexual reproduction does occur in lower animals such as amphibians,it has never been achieved in mammals before until very recently.