Fig. 1. Asymmetric histone H3 methylation of lysine 9 in the parental genomes of one-cell mouse embryos. Mouse GV-stage (GV) and MII-stage (MII) oocytes, one-cell embryos collected 3, 6 and 12 hours after in vitro fertilization (IVF 3, 6, 12 h) (A), and parthenogenetic and androgenetic one-cell embryos (B), were subjected to immunocytochemistry with antibody to methylated histone H3 Lys 9 (MeH3/K9). The antibody was localized with FITC-conjugated secondary antibodies (green), and DNA was stained with DAPI (blue). The parthenogenetic embryos were prepared by exposing MII-stage oocytes to 7% ethanol for 6 minutes, and collected for immunocytochemistry 6 hours later. The androgenetic embryos were prepared by fertilizing enucleated oocytes in vitro, and collected for immunocytochemistry 6 hours after fertilization. Arrows indicate the male (m) and female (f) pronuclei. pb, polar body. The experiments were conducted at least three times and similar results were obtained. More than 25 images were obtained for each type of embryo and representative examples are shown.