Figure 7. CpG ratios in the coding sequence of selected insects.CpG ratios were calculated using RefSeq data for each insect species. For
each sequence the observed (obs) CpG frequency and the expected (exp) CpG frequency were calculated. The expected CpG frequency was
calculated based on the GC content of each sequence and the CpG ratio was calculated as obs/exp. The frequency of each CpG ratio was plotted
against the observed/expected ratio. A bimodal distribution was observed forA. pisumandA. mellifera, both of which show DNA methylation within
the coding sequence of genes [37,129].D. melanogasterandT. castaneumboth show a unimodal distribution, and there is only limited evidence of
methylation in both of these species. In additionA. pisumandA. melliferahave all the DNA methyltransferases whileD. melanogasteronly hasDnmt2
andT. castaneumhasDnmt1andDnmt2.
doi:10.1371/journal.pbio.1000313.g007