Discrimination of methylation states based on direct bisulfite sequencing chromatograms. Direct sequencing of PCR products from the EFS CpG island from bisulfite treated DNA. The reverse sequence is shown here. Therefore, the A signals represent unmethylated cytosines, which have been converted to thymine during bisulfite treatment of genomic DNA and the G signals represent methylated cytosines. (A) The analyzed region was classified as showing "full methylation" if A-signals were absent at every CpG; (B) "no methylation" in the absence of G signals at every CpG position or (C) "partial methylation" if both signals were present at some or all CpG positions.