In the context of genomes, CG refers to CpG dinucleotides, which are particularly important because:
* Methylation: CpG dinucleotides are frequently methylated, meaning a methyl group (CH3) is added to the cytosine base. This methylation can play a role in regulating gene expression.
* Underrepresentation: CpG dinucleotides are underrepresented in the genome compared to what would be expected by chance. This is due to the high rate of mutations at CpG sites.
So, in essence, CG in genomes refers to CpG dinucleotides, which are important for methylation and gene regulation.
