DNA is made up of a repeating set of chemicals usually abbreviated as A, G, C, and T. These letters are the raw stuff of genes. Each gene has a certain number of these letters in a certain order.

A gene has the instructions for making a specific protein. Each of these proteins then does a specific job in the cell. They carry oxygen, help digest our food, and let us see, hear, breathe and even think.

One way that people are different is in the letters of their DNA. On average, one person has around 6 million different letters (out of 6 billion) compared to someone else.

If one of these differences is in a gene, it can cause the protein to be made to act differently. For example, this kind of change can cause one person to make a protein that causes brown eyes. Or it can cause another person to make a protein that gives him or her blue eyes.

Another reason people are different is in how they use their genes. Some people might have a certain gene turned way up so that it makes lots of protein. Others might have the same gene turned down so they make less protein.

Part of this can come from differences in letters. But part can come from differences in methylation too.

Methylation can hide a gene from the cell making it harder to read. This means that a methylated gene gets read less often or not at all. Which means little or even no protein gets made. So changes in methylation might cause changes in how some genes are used.

How DNA Can Change

The letters of DNA that we are born with don't change much over our lifetime. There is an occasional change but it is pretty rare.

Methylation is thought to be a different matter though. Scientists think that methylation can change a lot in the DNA of any cell.



DNA letters can change like this.

Methylation can change as well.

Scientists know that as a fertilized egg develops into a human, different genes get methylated and unmethylated. The new patterns of methylation are a big part of determining whether a cell turns into skin, muscle, nerve, etc.

Scientists also know that at least in mice, what mom eats can affect how a pup's DNA is methylated. The same is thought to be true in people too.

So there are definitely methylation changes that can happen in the womb. But what about afterwards?

A recent study showed that each twin in an identical twin pair has different DNA methylation. What this suggests is that the environment we live in can affect how our DNA works. It also suggests that as we age, our DNA methylation pattern changes. Now this new report confirms it.

The researchers showed that methylation can change with age by looking at two different groups. The first was a group of 111 Icelanders. The second was 126 people from Utah.