Final answer:
DNA is typically methylated at the promoter region within CpG islands, which can lead to gene silencing by impacting protein interactions and transcription control.
Step-by-step explanation:
The area of DNA that is typically methylated is the promoter region. DNA methylation occurs within specific regions called CpG islands, which are stretches with a high frequency of cytosine and guanine dinucleotide pairs (CG) found predominantly in promoter regions of genes. The methylation of cytosine in CpG islands within the promoter region can lead to silencing of the gene, as the modification alters how DNA interacts with proteins, including the histone proteins that control access to the region, therefore affecting transcription initiation.