The 6-mer sequences found most frequently (top 5) in the upstream and downstream regions in actively
expressed genes. All 6-mer sequences (n = 4,096) were searched for in the 1,000 bp upstream and 200 bp
downstream regions of the TSS of actively expressed genes in preimplantation embryos, oocytes and
tissues. Subsequently, the number of the genes that had each of the 6-mer sequences was determined. The
sequences that were found most frequently (top 5) in each embryo, oocyte and tissue are listed. The
sequences that were identical to those of the 1-cell stage embryos were marked with the same color as
that of the 1-cell stage embryos.