( Identical twins lose some fundamental s...)Identical twins may have more differences than meet the eye

They may start to look and act less alike. The changes could leave one twin susceptible to diseases like cancer, while the other twin remains healthy.

Researchers report in this week's Proceedings of the National Academy of Sciences that these differences may stem from changes in the epigenome. The epigenome refers to chemical modifications in genes that don't directly affect a gene's DNA but result in changes in gene expression.

Scientists think that chemical exposure, dietary habits and environmental factors may all have epigenetic affects.

Most epigenetic changes are normal and may explain why pairs of twins lose some of their identical attributes as they age. But learning how these modifications affect cells may also shed light on how cancer progresses and develops, said Christoph Plass, a study co-author and an associate professor of molecular virology, immunology and medical genetics at Ohio State University .

Plass and Yue-Zhong Wu, a research associate also at Ohio State , helped a team of European scientists analyze epigenetic changes in twins' genomes. The group was led by Manel Esteller, a researcher with the Spanish National Cancer Center in Madrid .

The researchers studied 40 pairs of twins recruited in Spain , Denmark and the United Kingdom ; 25 of the pairs were female. The youngest set of twins was 3, and the oldest pair was 74. All of the participants were asked to complete questionnaires about their health, eating habits, physical activity, history of prescription medication use and tobacco, alcohol and drug consumption.

The researchers also drew blood samples from each participant in order to analyze and compare similarities and differences in the epigenome.

Results from the blood tests ?and from the questionnaires ?showed that the youngest set of twins had the most identical genomes. But that w
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Source:Ohio State University