Figure 2.

Correspondence between DNA methylation and CpG O/E. (a) CpG O/E calculated in 500 bp sliding windows in the human chromosome 1 is inversely related to empirically measured DNA methylation in the human brain. Human chromosomes are generally hypermethylated and exhibit low CpG O/E. Regions devoid of DNA methylation maintain relatively high CpG O/E and are referred to as ‘CpG islands’. (b) CpG O/E and DNA methylation in honeybee. Honeybee chromosomes are generally devoid of DNA methylation, with the exception of peaks of DNA methylation observed in the so-called methylation islands [16]. CpG O/Es are generally high in the honeybee genome and show a reduction in regions corresponding to methylation islands. (Online version in colour.)