April 24th, 2006

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Identical twins may have less in common than they think


A study now shows that the expression of their genes gets more and more different with age.
The findings could help to explain why one twin may develop a genetically influenced disease, such as diabetes, while the other remains perfectly healthy.

Identical twins have identical genes, because they are born of an embryo that splits at a very early stage in development. Such twins are often indistinguishable in outward appearance. But over the course of time they may experience radically dissimilar health.

Most scientists have assumed that environmental and lifestyle differences cause such divergence. These things trigger chemical reactions that affect our DNA and the proteins entwined with our DNA, called histones. One such reaction, known as methylation, influences the expression of genes and so can have an impact on health.


"Most people had the hypothesis that changes in DNA methylation are effected by the environment," says lead author Mario Fraga of the Spanish National Cancer Centre in Madrid. "This is the first time that somebody has demonstrated that this is the case." The findings appear in the Proceedings of the National Academy of Sciences


Nature.com, July 2005
http://www.abc.net.au/news/newsitems/200507/s1407923.htm
http://multiples.about.com/od/funfacts/a/differenttwins.htm