New research from Europe and the US suggests that identical twins become less identical as the years go by. In a study of 80 sets of identical twins, the researchers found that there were significant epigenetic differences between those older twins, while younger pairs are still identical.

Epigenetics is the study of inheritable changes in gene function, or expression, that happen without a change in gene sequence. So while DNA sequences can be identical, the way those genes are expressed can vary from person to person. It is key to the study of many diseases, including cancers that appear to be caused when certain genes are inappropriately switched off.

The researchers hope the study, published in this week's Proceedings of the National Academy of Sciences, will further understanding of how the environment and our genes can interact to produce diseases and other differences between people.

"Our study reveals that the patterns of epigenetic modifications in (identical) twin pairs diverge as they become older," the researchers wrote, according to a Reuters report. "Most importantly, we found a direct association between the remarkable epigenetic differences observed and the age of the monozygotic (identical) twins: the youngest pairs were epigenetically similar, whereas the oldest pairs were clearly distinct."

The findings seem to support the idea that environmental factors - like smoking, diet exercise and so on - can have an effect on DNA. ®

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