Final answer:
Methylation can occur on cytosines that are followed by guanine bases, within CpG dinucleotides located in CpG islands. This process of DNA methylation leads to gene silencing and is an important aspect of gene regulation. It can also be influenced by external factors and inherited across generations.
Step-by-step explanation:
Methylation, an epigenetic modification with significant regulatory effects on gene expression, may occur on cytosines that are followed by guanine bases. In the context of DNA methylation, these cytosines are part of specific sequences called CpG dinucleotides, often concentrated within regions known as CpG islands. These islands are frequently located in gene promoter areas, influencing gene activity by modifying the interaction between DNA and various proteins, including histones.
The cytosine base within the CpG dinucleotide can undergo the addition of a methyl group, typically resulting in the silencing of the associated gene. DNA methylation is an integral part of gene regulation and can be influenced by environmental factors and be heritable, as certain methylation patterns can be passed down from parents to offspring, a phenomenon known as genomic imprinting.
Moreover, the array of biological processes influenced by methylation emphasizes its importance in development, cell differentiation, and disease pathology, making it a focal point of study in fields like genetics and epigenetics.