美国英语听力80篇3 Lesson59

（单词翻译）

[00:05.49]Physical changes, such as gray hair and small lines on the face, appear as we grow older.
[00:15.78]Now, American scientists say such changes may result partly from changes in our genetic¹ material.
[00:24.24]They say these genetic mutations increase over time as the cell-division process in our bodies begins to break down.
[00:34.77]Researchers from the Scripps Research Institute in La Jolla, California,
[00:41.56]reported the findings² in the publication³ Science.
[00:45.43]The researchers examined cells from four groups of people:
[00:50.76]normal children, adults, very old people and children with a genetic condition called progeria.
[01:01.65]Progeria causes the body to grow older at an extremely fast rate.
[01:08.15]The researchers used a new technology to examine more than 6,000 genes⁴ at once.
[01:16.88]They could see which genes were active among people in each age group.
[01:23.91]They found that most of the genes kept the same level of activity in youth,middle age and old age.
[01:34.04]However,the researchers identified sixty-one genes that speeded up or slowed down with age.
[01:42.19]Richard Lerner of the Scripps InstitUte helped organize the study.
[01:48.15]Mister Lerner says one-fourth of the sixty-one genes are what he calls quality control genes.
[01:56.58]He says they are supposed to prevent cells from dividing if there are mistakes in the genetic material.
[02:05.26]If the quality control genes work,then the genetic mutations are stopped immediately.
[02:12.65]But sometimes the cells with genetic matatiofis produce new cells with the same mistakes, or worse one.
[02:21.98]He says the increasing number of genetic mistakes in the cell-division process may cause signs of aging.