Methylation spreading.

The ρ-globin gene promoter and exon 1 (proximal transcribed) regions were amplified with a single set of primers with bisulfite-treated DNA from day 8 erythroid cells as a template. Positions indicated are relative to the transcription start site. Percentage methylation is indicated at CpG dinucleotides. Exon 1 is methylated to a greater degree as compared with the promoter region.