Final answer:
Methylation is typically higher in repetitive mobile elements across various species to suppress their activity, but bees exhibit unique methylation patterns that differ from this norm. DNA methylation and histone modification regulate gene expression by affecting nucleosome spacing.
Step-by-step explanation:
Methylation is typically higher in repetitive mobile elements in a genome, serving to suppress their activity and thus protect genomic integrity. However, this is not the case for bees, where methylation patterns differ from other species like plants, fishes, and mice. Methylation in bees is unique and does not follow the typical pattern observed in most other species.
DNA methylation and histone modification play a critical role in regulating gene expression by altering the spacing of nucleosomes. This, in turn, dictates whether a DNA region is transcriptionally active or silenced. In regions known as CpG islands (stretches of DNA with a high frequency of CG pairs) found in gene promoter areas, the addition of a methyl group to the cytosine base usually results in gene silencing, although this can lead to other regulatory effects as well.