Methylation status of CGI8b in preimplantation embryos. The methylation status of two-cell and blastocyst DNAs was analyzed in CGI8b. The presentation is basically the same as in Fig. 3C. Clones are grouped by separate PCRs. Independent experiments were performed several times; representative results are shown. The primers are described in Methods. F₁ hybrid embryos used here are all BPF₁.