题型：阅读理解 题类：常考题 难易度：普通
河北省邢台市2017-2018学年高二上学期英语第二次月考试卷
Conventional wisdom says that hardship can make us old before our time. In fact, a new study suggests that violence not only leaves long-term scars on children's bodies, but also changes their DNA, causing changes that are equal to seven to ten years of premature aging.
Scientists measured this by studying the ends of children's chromosomes (染色体), called telomeres (端粒), says Idan Shalev, lead author of a study published in Molecular Psychiatry.
Telomeres are special DNA sequences (序列) which prevent the DNA in chromosomes from separating. They get shorter each time a cell divides, until a cell cannot divide any more and dies.
Several factors have been found to shorten telomeres, including smoking, radiation and psychological stresses such as being treated badly when young and taking care of a chronically ill person.
In this study, researchers examined whether exposure to violence could make children's telomeres shorten faster than normal. They interviewed the mothers of 236 children at ages 5, 7 and 10, asking whether the youngsters had been exposed to domestic violence between the mother and her partner; physical maltreatment by an adult; or bullying. Researchers measured the children's telomeres-in cells obtained by wiping the insides of their cheeks-at ages 5 and 10.
Telomeres shortened faster in kids exposed to two or more types of violence, says Shalev. Unless that pattern changes, the study suggests, these kids could be expected to develop diseases of aging, such as heart attacks or memory loss, seven to 10 years earlier than their peers.
Shalev says there is hope for these kids. His study found that, in rare cases, telomeres can lengthen. Better nutrition, exercise and stress reduction three things that may be able to lengthen telomeres, he says.
The study confirms a small but growing number of studies suggesting that early childhood a adversity imprints itself in our chromosomes, says Charles Nelson, a professor of pediatrics and neuroscience at Harvard Medical School.
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