听力文本

Study: Identical Twins Are Not Genetically Exact Copies
A new study suggests that identical twins are not exactly the same genetically. Identical twins are two babies that come from the same fertilized egg.
Scientists in Iceland examined DNA from 387 pairs of identical twins, their parents, children, husbands or wives.
The examinations led the team to find "early mutations that separate identical twins," lead researcher and geneticist Kari Stefansson said. He is a professor at the University of Iceland and founder of the company deCODE genetics.
Mutations are small changes in DNA that can happen when a cell divides in an attempt to copy itself. These small changes can influence a person's physical appearance or control a person's ability to fight a disease.
The newly-discovered mutations show that identical twins do have genetic differences, the researchers said. The results were recently published in Nature Genetics.
On average, identical twins have 5.2 of these early genetic differences, the researchers found. But about 15 percent of identical twin pairs have more than that. Some might have as many as 100 genetic differences, Stefansson said.
These differences represent a small part of each twin's genetic material. But they could influence why one twin is taller or why one is at greater risk for some cancers than the other.
In the past, many researchers believed physical differences seen in identical twins were related mostly to environmental influences, such as nutrition or lifestyle behaviors.

Jan Dumanski is a geneticist at Sweden's Uppsala University. He was not involved in the study. He praised the findings as "a clear and important contribution" to medical research.
"The implication is that we have to be very careful when we are using twins as a model" for examining the influences of genetics or the environment, Dumanski said.
A 2008 paper in The American Journal of Human Genetics found some genetic differences between identical twins. The new study, however, goes beyond earlier work by including the DNA of parents, children, husbands and wives of identical twins.
Studying family members permitted the researchers to examine when genetic mutations happened in two different kinds of cells: those present in only one individual and those passed on to the person's children.
Stefansson said his team found twins where a mutation is present in all cells of the body of one twin, but not in the other twin at all. However, "sometimes the second twin may show the mutation in some cells, but not all cells," he added.
The researchers said they also found mutations that came about before the developing embryo split in two.
Nancy Segal is a psychologist who studies twins at California State University, Fullerton. She was not involved in the study. But she called the results "heroic and really significant."
Segal added that the research is likely to persuade more scientists to rethink the influences of genetics and environment on twins. "Twins are very alike, but it is not a perfect similarity," she said.
I'm Bryan Lynn.

重点解析

重点讲解：
1. permit sb. to do sth. 允许；准许；
This permitted Western manufacturers to play their strong cards: capital and technology.
这让西方制造商得以亮出他们的王牌：资金和技术9LQAIw[uz4,AzOdebu。
2. pass on to 将…传给；将…交给；
It may cause illness that could be passed on to our children and grandchildren.
它还可能引起某种疾病，而这种疾病又可遗传给我们的子孙后代n;FAUD[36wF[。
3. come about 产生；发生；
How did this unhappy state of affairs come about?
这种不幸的情况是怎么发生的呢？
4. persuade sb. to do sth. 劝说；说服；
You'll never persuade him to stay ─ his mind's made up.
你根本无法劝他留下来——他已经拿定主意了7H=O+^.t);#pL;D。

参考译文

研究表明同卵双胞胎的基因并不完全相同
一项新研究表明，同卵双胞胎的基因并不完全相同sW2phB1Vr3~YIQjOde。同卵双胞胎是来自同一受精卵的两个胎儿81iA[fkf!iTF。
冰岛科学家387对同卵双胞胎及其父母、子女和配偶的DNA进行了测序vG[M,]oq-55CVn7)。
首席研究员和遗传学家卡里·斯特凡松表示，检测使研究小组发现了“分离同卵双胞胎的早期突变”p;DHytXTIF]i2CN。斯特凡松是冰岛大学的教授，也是deCODE genetics公司的创始人tgGlE&fJ[RleYbR。
突变是细胞分裂试图复制时，可能发生的DNA的微小变化9aMGDqg3^8。这些微小变化可以影响一个人的外表或控制一个人抵抗疾病的能力*K(v-5]gJXv0。
研究人员表示，新发现的突变表明同卵双胞胎确实存在基因差异4u@!Fz&OKya5Yq7K。研究结果最近发表在《自然·遗传学》期刊上rx.g@-lUa^yG-3。
研究人员发现，同卵双胞胎的早期基因差异平均相差5.2个p^r^ldz^LK[q];[q。但是大约有15%的同卵双胞胎的差异更大npF7k~~uLf[Gh。斯特凡松表示，有些双胞胎之间可能有多达100个基因差异^4!Qp=6bHP2*G,。
这些差异代表了每对双胞胎遗传物质的一小部分&n2c@8wJ(!a4SQl9Bp。但是可能会产生相当大的影响，比如双胞胎中一人比另一人高，或一人患癌症的风险要大于另一人9O^d~s#!gqZ+c4=p^4W。
过去，许多研究人员认为，同卵双胞胎的生理差异主要与环境影响有关，如营养或生活习惯等]DF=bbhkNHaWb|。
扬·杜曼斯基是瑞典乌普萨拉大学的遗传学家]pTTF.zzcCuBnxdSpRd。他没有参与这项研究#pC4+1ePbaE4。他称赞这一发现为医学研究做出了“明确而重要的贡献”dX-dcupOY~_c-K。
杜曼斯基说，“这意味着，我们将双胞胎作为研究基因或环境影响的模型时，必须非常谨慎小心MXWv3fy|fNLrX7v。”
2008年发表在《美国人类遗传学杂志》上的一篇论文发现了同卵双胞胎之间的部分基因差异j98xlCW)gD@。然而，这项新研究超越了早期的工作，纳入了同卵双胞胎的父母、孩子和配偶的DNA研究ys%17Hv0X%6_x。
通过对家庭成员的研究，研究人员可以检测两种不同类型的细胞何时发生基因突变：一种是只存在于个人身上的细胞，另一种是遗传给孩子的细胞kbWQo|Zwt1(7[6JSx。
斯特凡松表示，他的研究小组发现了一对双胞胎，其中一个体内所有细胞都发现了突变，而另一个则完全没有1i,8ZugCelvM_QYOm3K2。然而，他补充说，“有时双胞胎中的另一个可能会在某些细胞中出现突变，而是不是所有细胞都突变-2n1_tJK!HL.FS。”
研究人员表示，他们还发现了发育中的胚胎在分裂成两半之前发生的突变))i5aNR3kwRGziI(cJ。
南希·西格尔是心理学家，她在加州州立大学富勒顿分校研究双胞胎dCFX3mlOl~n。她没有参与这项研究QcjVn*tq8Z。但她称研究结果“是项壮举，具有重要意义”Negb4tVfGdUjg|E^il9j。
西格尔补充说，这项研究可能会说服更多的科学家重新思考基因和环境对双胞胎的影响lCOJp,[xY(1+5c|x(b-3。她说，“双胞胎长得很像，但并不是完全一样ej#T52=dl*zXC,4A)Ae。”
布莱恩·林恩报道B8@O4gDfaF2oZ^,#&。

译文为可可英语翻译，未经授权请勿转载！