Three major categories of animal methylomes. Ubiquitous, sporadic and absent DNA methylation (5mC) are illustrated with three examples from whole-genome bisulfite sequencing analyses of mouse (top), honey bee (middle) and Drosophila DNA (bottom). Methylation ratios for each CpG dinucleotide in a randomly selected 40 kB window are shown. Gene features are indicated below each panel. Transparent blue bars indicate the range of bisulfite conversion artifacts (methylation ratios below 0.2).