What is DNA methylation?

DNA methylation is when methyl groups are added to a strand of DNA which can regulate the activity of the DNA without changing the sequence by turning the DNA “on” or “off”.

How does DNA methylation occur?

Methylation of DNA occurs when an enzyme, known as a DNA methyltransferase, adds a methyl group to a cytosine base in the DNA sequence. This addition of a methyl group can affect the expression of the gene by turning the gene on and off. 

Where does DNA methylation take place? 

A specific part of DNA, the cytosine base, is where DNA methylation has been found to occur. This takes place in the nucleus of the cell, where DNA is located. 

How does DNA methylation affect gene expression?

DNA methylation can cause a gene to be turned “on” or “off.” When DNA is methylated, it typically turns the gene off, causing it to not be expressed. When DNA is demethylated, it turns on, causing the gene to be expressed. This change in gene expression without changing the DNA sequence is known as epigenetics.