Final answer:
CpG islands near housekeeping genes are generally unmethylated, allowing these essential genes to be actively transcribed for basic cellular functions.
Step-by-step explanation:
In the context of DNA methylation, CpG islands are regions with a high frequency of cytosine and guanine dinucleotides ([CG] pairs) often found in the promoter regions of genes. In particular, CpG islands near housekeeping genes are generally unmethylated to ensure that these genes are actively transcribed. Housekeeping genes are essential for the maintenance of basic cellular functions and are typically expressed in all cells, hence their DNA must be accessible to transcription machinery.
When CpG sites within these islands are methylated, it typically leads to the silencing of the gene. The presence of unmethylated CpG islands is essential to keep housekeeping genes active. Contrarily, methylated regions of DNA, along with deacetylated histones, result in a tightly coiled chromatin structure that is transcriptionally inactive, which is a condition often observed in silenced genes in cancer cells.