Bisulfite direct sequencing of EP6. The asterisk represents CpG sites in EP6. Red and blue peaks in sequences indicate T and C bases, respectively. Red (T) and violet (H) characters represent unmethylated cytosine and heterozygous cytosine, respectively, in CpG sites. CpG sites of EP6 were completely unmethlylated in normal pregnant blood (A) and were hypermethylated in both normal placenta (B) and trisomy 21 placenta (C).