Question

DNA methylation may be a significant mode of genetic regulation in eukaryotes. Methylation refers to ________.

A) altering RNA polymerase activity by DNA modifications
B) changes in DNA-DNA hydrogen binding
C) altering translational activity especially of highly methylated tRNAs
D) alteration of DNA polymerase activity by addition of methyl groups to glycine residues
E) addition of methyl groups to the cytosine of CG doublets

Answer 1

DNA methylation refers to the addition of methyl groups to cytosine bases within CG doublets, often leading to gene silencing and playing a key role in genetic regulation.

Step-by-step explanation:

DNA methylation is a significant mode of genetic regulation in eukaryotes. Specifically, methylation refers to the addition of methyl groups to the cytosine of CG doublets. These CG doublets are often located in CpG islands, which are regions with a high frequency of cytosine and guanine pairs within the promoter regions of genes. When these cytosines are methylated, the gene is usually silenced or its expression is lowered. This epigenetic modification can impact how DNA interacts with various proteins, including histones that control the access to regions of DNA, and can thus play a role in regulating gene transcription. Methylation patterns can also be heritable, being maintained through cell divisions and even passed on to offspring, illustrating how environmental factors can have long-term genetic effects.