在遗传中，基因会发生改变甚至突变，这是我们都知道的。可最近冰岛一家研究中心指出，在人的一生中，年龄的增长，环境的变化，营养的变化也会导致基因发生改变。

    Individual human genomes change throughout a person's life influenced by environmental or nutritional factors which may explain why illnesses such as cancer come with age, a study said Tuesday.

    Researchers at Johns Hopkins University found that the so-called epigenetic marks on the sequence of a person's DNA modify over the course of their life and the extent of such changes is similar among family members.

    "We're beginning to see that epigenetics stands at the center of modern medicine because epigenetic changes, unlike DNA sequence which is the same in every cell, can occur as a result of dietary and other environmental exposure," said Andrew Feinberg, professor of molecular biology and genetics at the university.
    
    "Epigenetics might very well play a role in diseases like diabetes, autism and cancer," he added in the study published in the Journal of the American Medical Association.

    The team analyzed the DNA sequences from 600 people taking part in the AGES Reykjavik (雷克雅维克，冰岛首都) Study, formerly called the Reykjavik Heart Study in Iceland.

    The participants supplied DNA samples in 1991, and then again between 2002 and 2005.

    Scientists then measured the variations in the levels of methylation (甲基化), which is the main epigenetic modification, in 111 samples. In about a third of cases, the methylation levels had changed over the years.

    "Inappropriate methylation levels can contribute to disease -- too much might turn necessary genes off, too little might turn genes on at the wrong time or in the wrong cell," said Vilmundur Gudnason, professor of cardiovascular (心脏血管的) genetics at the University of Iceland.

    "What we saw was a detectable change over time, which showed us proof of the principle that an individual's epigenetics does change with age," added Daniele Fallin, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.

    Such changes could also be hereditary, which might explain why some families are more affected by certain diseases than others.