Maturation and manipulation of mouse oocytes and the resulting outcomes: cumulus-enclosed germinal vesicle (GV) oocytes (A), denuded GV oocytes (B), matured oocytes (C), complete enucleation of germinal vesicle oocyte (D), complete enucleation of cumulus-enclosed germinal vesicle oocyte (E), selective enucleation of g germinal vesicle oocyte (F), enucleation of pro-metaphase I oocyte (G), enucleation of metaphase I oocyte (H), enucleation of metaphase II oocyte (I) enucleolation of germinal vesicle oocyte (J), fetal fibroblast (K), germinal vesicle karyoplasts (L) GV karyoplasts placed under the zona pellucida of enucleated GV oocytes (M) fused with cytoplasts (N, O) developed zygote upon embryonic nuclear transfer (P), developed hatching blastocyst upon embryonic nuclear transfer (Q) offspring upon fallopian embryo transfer.