Answer:
This event, called methylation, usually stops or represses the expression of a gene.
Step-by-step explanation:
The expression of the gene can be controlled by an event which adds the methyl group to the DNA molecule especially in the histone proteins called Methylation.
The addition of the methyl group to the nitrogenous bases is a common event in both prokaryotes and eukaryotes.
If methylation takes place in the promoter region of the gene then it represses the transcription of a gene or the gene is suppressed.
Thus, the selected option is correct.