Gel-electrophoresis image of TET1 gene that PCR amplified from embryonic DNA. The size of amplified region of wild-type TET1 gene is 431 bp. The first lane is a size marker. The target regions were successfully amplified from single blastomeres (lane 2-5) of a 4-cell embryo. The four blastomeres were isolated from an identical 4-cell embryo. The target region was also amplified in a whole 4-cell embryo (lane 6) and blastocyst (lane 7). BM, blastomere; BL, blastocyst.