Final answer:
Unmethylated CpG islands are actually associated with active genes, not inactive ones. Methylation of CpG islands leads to gene silencing, especially when accompanied by histone deacetylation. This mechanism is important in understanding the regulation of gene expression in both normal and diseased states, such as cancer.
Step-by-step explanation:
The statement that unmethylated CpG islands are correlated with inactive genes is actually a misconception. In reality, CpG islands are regions in DNA with a high frequency of cytosine and guanine pairs, often found near gene promoters. When the cytosines of CpG islands are methylated, it typically leads to gene silencing. This methylation, along with chemical modifications of histones such as deacetylation, causes the DNA to be tightly packed and thereby transcriptionally inactive. However, when CpG islands are not methylated, the associated genes are usually active.
For instance, in cancer cells, epigenetic alterations often include the methylation of CpG islands and deacetylation of histones, leading to the silencing of genes that are typically active. Such patterns can sometimes be reversed, providing avenues for therapeutic interventions. Besides its role in diseases, DNA methylation can be influenced by environmental conditions and processes such as genomic imprinting.