What is DNA Methylation?

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  • Written By: Daniel Liden
  • Edited By: Jenn Walker
  • Last Modified Date: 29 November 2016
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DNA methylation is the biological process by which a methyl group, which is an organic functional group with the formula CH3, is added to DNA nucleotide. DNA, or deoxyribonucleic acid, is an important nucleic acid that stores the genetic information for any given organism. It is made up of four different molecules known as nucleotides; these are referred to as adenine, cytosine, guanine, and thymine. Through DNA methylation, a methyl group can be attached to a carbon atom on cytosine or to a nitrogen atom on adenine. The addition of a methyl group to these nucleotides can serve many important biological purposes, such as suppressing potentially harmful viral genetic information that is present in the human genome.

The DNA in many different types of organisms can undergo DNA methylation, though it does not always necessarily serve the same function. In plants, for example, scientists believe that methylation occurs to deactivate genes that could otherwise cause harmful mutations. In fungi, this process is used to moderate and control the expression of certain genes based on the particular conditions affecting the fungus. Methylation in mammals similarly moderates and inhibits the expression of certain genes; additionally, it is involved in the production of chromatin, a protein-DNA complex that makes up the structure of chromosomes.


Various enzymes, or proteins that catalyze biochemical reactions, are required in order to attach a methyl group to DNA nucleotides. The specific family of enzymes necessary for DNA methylation is known as DNA methyltransferase. DNA methylation tends to follow a pattern; once a nucleotide is methylated, copies of that nucleotide will also be methylated after DNA replication that occurs normally over the course of cell division. De novo methyltransferases are responsible for the initial methylation that occurs during early development. Maintenance methyltransferases add methyl groups to nucleotides that are produced through DNA replication; they ensure that copies of methylated DNA are also methylated.

Scientists use many different methods to detect DNA methylation in samples of DNA. Such methods can be used to determine the methylation of a given strand of DNA and to determine which specific genes are affected by methylation. The two main goals of the various DNA methylation analysis techniques are profiling and typing. Profiling is aimed at characterizing the methylation of an entire genome or similarly large genetic sample. Typing is aimed at examining the methylation of a few genes or DNA segments over many samples to ensure accuracy and to detect differences in different samples.


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Post 4

Does DNA methylation always happen on its own or can scientists cause methylation as well?

Genetic engineers are able to do so many things with DNA these days. They can split DNA and put it back together or clone it if they want. I wonder if scientists can add a methyl group to DNA and cause methylation artificially?

Post 3

DNA methylation is part of the curriculum for epigenetics. Most people don't hear about this too much unless they study molecules and genetics. My dad is a Professor of this and he has a lecture book on gene silencing.

He has me help with his class slides sometimes because he prefers to talk and I prefer to type! That's where I learned about epigenetics. My dad's notes say that epigenetics is the study of how genes function and change based on our DNA which is inherited from our parents. Methylation also has to do with gene silencing, where, as this article also mentioned, we carry many genes which are turned off and don't function.

I've never asked my

dad about this but I think epigenetics implies that DNA methylation is also something we inherit from our parents. Our genes determine which genes are meant to be on and which are meant to be off and cause methylation according to that.

DNA methylation, along with something called histone modification, determine how our DNA, and the genes in our DNA act. I think histones are a type of protein that acts similarly to methyl groups. Just like in metyhlation, histones can attach themselves to DNA and impact how they function.

What's most interesting to me out of all of this is that everything that goes on in our body- including individual hydrocarbons that make up a methyl group- is inherited from our parents. It's so interesting!

Post 2

I recently heard about DNA methylation in a magazine which was doing a special issue on cancer. It said there that some scientists are blaming DNA methylation for turning off genes that suppress cancer cells, which makes the cancer grow and get out of hand more quickly. Other scientists claim that methylation is actually the result of the turning off of these cancer suppressing genes and not the cause.

I'm not really sure what this all means or which argument is more correct. But clearly, DNA methylation is pretty important for cancer patients, because it might putting them at greater risk of not surviving cancer.

I sure hope that more research is done on this to figure what

exactly the connection is between DNA methylation and cancer. And if it is playing a role in the development of cancer cells, I hope something can be done about it. I think this is important not just for patients who already have cancer but also healthy individuals who may be at risk for it.
Post 1

I had to study about this for one of my classes and as far as I understand, DNA methylation is one of the things that scientists need to keep an eye on to control gene activity.

In simple terms, different genes in our body have different purposes. But the most important role of genes is to both attack and protect themselves. If an an "enemy DNA" like a virus is in the body, the cells need to attack it to prevent it from entering the cell. But this also has to be under control so that the body doesn't start to kill its own cells. So there has to be some offense and defense going on at the same


Methyltransferases are the ones on the defense, protecting the DNA from unknown intruders. If the balance between defense and offense is off for some reason, then things will start going wrong. So if there is too much or too little DNA methylation, then the DNA will either be overprotected, or not protected enough. That's why scientists will want to look at DNA methylation in an organism to see if it is working at the right rate.

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