Research using twins
To biomedical researchers all over the world, twins offer a precious opportunity to untangle the influence of genes and the environment — of nature and nurture. Because identical twins come from a single fertilized egg that splits into two, they share virtually the same genetic code. Any differences between them — one twin having younger looking skin, for example — must be due to environmental factors such as less time spent in the sun.
Alternatively, by comparing the experiences of identical twins with those of fraternal twins, who come from separate eggs and share on average half their DNA, researchers can quantify the extent to which our genes affect our lives. If identical twins are more similar to each other with respect to an ailment than fraternal twins are, then vulnerability to the disease must be rooted at least in part in heredity.
These two lines of research — studying the differences between identical twins to pinpoint the influence of environment, and comparing identical twins with fraternal ones to measure the role of inheritance — have been crucial to understanding the interplay of nature and nurture in determining our personalities, behavior, and vulnerability to disease.
The idea of using twins to measure the influence of heredity dates back to 1875, when the English scientist Francis Galton first suggested the approach (and coined the phrase ‘nature and nurture’). But twin studies took a surprising twist in the 1980s, with the arrival of studies into identical twins who had been separated at birth and reunited as adults. Over two decades 137 sets of twins eventually visited Thomas Bouchard’s lab in what became known as the Minnesota Study of Twins Reared Apart. Numerous tests were carried out on the twins, and they were each asked more than 15,000 questions.
Bouchard and his colleagues used this mountain of data to identify how far twins were affected by their genetic makeup. The key to their approach was a statistical concept called heritability. In broad terms, the heritability of a trait measures the extent to which differences among members of a population can be explained by differences in their genetics. And wherever Bouchard and other scientists looked, it seemed, they found the invisible hand of genetic influence helping to shape our lives.
Lately, however, twin studies have helped lead scientists to a radical new conclusion: that nature and nurture are not the only elemental forces at work. According to a recent field called epigenetics, there is a third factor also in play, one that in some cases serves as a bridge between the environment and our genes, and in others operates on its own to shape who we are.
Epigenetic processes are chemical reactions tied to neither nature nor nurture but representing what researchers have called a ‘third component’. These reactions influence how our genetic code is expressed: how each gene is strengthened or weakened, even turned on or off, to build our bones, brains and all the other parts of our bodies.
If you think of our DNA as an immense piano keyboard and our genes as the keys — each key symbolizing a segment of DNA responsible for a particular note, or trait, and all the keys combining to make us who we are — then epigenetic processes determine when and how each key can be struck, changing the tune being played.
One way the study of epigenetics is revolutionizing our understanding of biology is by revealing a mechanism by which the environment directly impacts on genes. Studies of animals, for example, have shown that when a rat experiences stress during pregnancy, it can cause epigenetic changes in a fetus that lead to behavioral problems as the rodent grows up. Other epigenetic processes appear to occur randomly, while others are normal, such as those that guide embryonic cells as they become heart, brain, or liver cells, for example.
Geneticist Danielle Reed has worked with many twins over the years and thought deeply about what twin studies have taught us. ‘It’s very clear when you look at twins that much of what they share is hardwired,’ she says. ‘Many things about them are absolutely the same and unalterable. But it’s also clear, when you get to know them, that other things about them are different. Epigenetics is the origin of a lot of those differences, in my view.’
Reed credits Thomas Bouchard’s work for today’s surge in twin studies. ‘He was the trailblazer,’ she says. ‘We forget that 50 years ago things like heart disease were thought to be caused entirely by lifestyle. Schizophrenia was thought to be due to poor mothering. Twin studies have allowed us to be more reflective about what people are actually born with and what’s caused by experience.’
Having said that, Reed adds, the latest work in epigenetics promises to take our understanding even further. ‘What I like to say is that nature writes some things in pencil and some things in pen,’ she says. Things written in pen you can’t change. That’s DNA. But things written in pencil you can. That’s epigenetics. Now that we’re actually able to look at the DNA and see where the pencil writings are, it’s sort of a whole new world.’
此类题目查考生对于文章细节的把握与辨别能力，考查题目中细节信息和逻辑关系是否与文章完全对应。因此在解题时，先要确保读懂题目，准确理解题目的意思，然后根据题目定位词回到原文相关内容与题目进行对照判断。
?1. There may be genetic causes for the differences in how young the skin of identical twins looks.
答案：FALSE
解析：找到关键词 “skin”对应到原文第一段， “Any differences between them – one twin having younger looking skin, for example – must be due to environmental factors such as less time spent in the sun.”原文说同卵双胞胎的皮肤存在差异性一定是由环境因素造成的，与题目中的may be genetic causes矛盾，所以答案为FALSE。
?2. Twins are at greater risk of developing certain illnesses than non-twins.
答案：NOT GIVEN
解析：根据关键词 “certain illness”定位到第二段If identical twins are more similar to each other with respect to an ailment than fraternal twins are, then vulnerability to the disease must be rooted at least in part in heredity. 原文中只是对同卵双胞胎和异卵双胞胎进行了对比，并没有提到非双胞胎non-twins。题干内容属于无中生有，所以答案为NOT GIVEN。
?3. Bouchard advertised in newspapers for twins who had been separated at birth.
答案：NOT GIVEN
解析：根据题目人名Bouchard和关键词 “separated”定位到第四段over two decades 137 sets of twins eventually visited Thomas Bouchard’s lab in what became known as the Minnesota Study of Twins Reared Apart. 这道题考察了separate和apart的同义词替换，原文中的确提到了此人做了双胞胎分离的研究，但并没有提及采用什么方式召集双胞胎，因此原文中的advertised in newspapers属于无中生有，所以答案为NOT GIVEN。
?4. Epigenetic processes are different from both genetic and environmental processes.
答案：TRUE
解析：根据关键词 “epigenetic”“genetic”“environmental”定位到第七段 Epigenetic processes are chemical reactions tied to neither nature nor nurture. 这道题很容易根据文章段落的顺序定位到第六段，虽然第六段中也提到了这几个关键词，但表达意思与题目完全不符，所以我们需要找其它定位，第七段中同样也有这三个词出现，意思是表观遗传过程与先天和后天都不相关的化学反应。题目同时也考察了一组同意替换different from和tied to neither，因此答案为TRUE。
二.信息匹配
此类题型属于细节题，重点考查考生提取信息的能力。可先将题干中的定位词在文中划出来，找到人名出现的答案句，寻找同义替换的选项。
?5. invented a term used to distinguish two factors affecting human characteristics
答案：A (Francis Galton)
解析：先确定题目中给出的人名有哪些，带着人名在文章中作出标记，方便快速定位。第四段提到The idea of using twins to measure the influence of heredity dates back to 1875, when the English scientist Francis Galton first suggested the approach (and coined the phrase ‘nature and nurture’.)”英国科学家FG首次提出这种方法，并提出了“先天和后天”这一方法。
?6. expressed the view that the study of epigenetics will increase our knowledge
答案：C (Danielle Reed)
解析：对应原文十二段“Reed adds, the latest work in epigenetics promises to take our understanding even further”. R表示，表观遗传学最新的研究将进一步加深我们的理解。上段中也提到了表观遗传学改变了人们对心脏病和精神分裂的看法。也就是此遗传学将提升我们的知识，确定答案为C。
?7. developed a mathematical method of measuring genetic influences.
答案：B
解析：定位到第五段，Bouchard and his colleagues used this mountain of data to identify how far twins were affected by their genetic makeup. The key to their approach was a statistical concept called heritability. In broad terms, the heritability of a trait measures the extent to which differences among members of a population can be explained by differences in their genetics.这道题的破题点在于statistical和mathematical对应。只要锁定了这组同意替换，就可以轻松选对答案B。
?8. pioneered research into genetics using twins
答案：A
解析：定位到第五段The idea of using twins to measure the influence of heredity dates back to 1875, when the English scientist Francis Galton first suggested the approach…，同意替换pioneered(做先驱) 对应first，因此答案为A。
?9. carried out research into twins who had lived apart
答案：B (Thomas Bouchard)
解析：第四段, .. twin studies took a surprising twist in the 1980s, with the arrival of studies into identical twins who had been separated at birth and reunited as adults. Over two decades 137 sets of twins eventually visited Thomas Bouchard’s lab…. 关键词apart，出生之后分开的双胞胎研究是TB展开的，因此答案为B。
三.句子填空
此类题型属于细节题，注意题目中的定位信息，同义替换及预测答案的可能词性。
?Question 10 and 11：In epigenetic processes, 10 __________ influence the activity of our genes, for example in creating our internal 11 ____________.
答案：10. D (chemicals) 11. B (organs)
解析：
10. 根据关键词epigenetic对应对应第七段，根据influence定位到theses reactions influence how our genetic…这句话，由此确定reactions，选项中的chemical reactions指代原文中的these reactions。
11. 定位第七段These reactions influence how our genetic code is expressed: how each gene is strengthened or weakened; even turned on or off, to build our bones, brains and all other parts of our bodies. 顺着第十题往下看，原文中列举了骨头、大脑和其它身体部位，这些都为身体器官，对应B选项中的organs。
?Question 12: The study of epigenetic processes is uncovering a way in which our genes can be affected by our ________.
答案：E (environment)
解析：根据关键词 “way”“uncovering”对应第九段One way the study of epigenetics is revolutionizing our understanding of biology is by revealing a mechanism by which the environment directly impacts our genes. affect和impact属于同义替换，因此答案为E。
?Question 13: One example is that if a pregnant rat suffers stress, the new-born rat may show problems in its ____________.
答案：F (behavior/ behavior)
解析：根据关键词stress对应第九段Studies of animals, for example, have shown that when a rat experiences stress during pregnancy, it can cause epigenetic changes in a fetus that lead to behavioral problems as the rodent grows up. 题目和原文都有problem，锁定behavioral，确定选项F。
剑桥雅思11 test4阅读词汇
precious adj. 珍贵的
virtually adv. 事实上，几乎
alternatively adv. 或者，另外
quantify v. 量化
pinpoint v. 确定，指出精确位置
inheritance n. 遗传
rear v. 养育
trait n. 特点，属性
invisible adj. 看不见的
radical adj. 重大的，彻底的
component n. 组成部分
heritability n. 遗传可能性
immense adj. 巨大的
segment n. 片段，部分
revolutionize v. 革新
reveal v. 揭示
pregnancy n. 怀孕
randomly adv. 随机地
surge n./v. 激增
reflective adj. 思考的，反思的
剑桥雅思11 test4长难句
1. [Alternatively], [by comparing the experiences (of identical twins) with those (of fraternal twins, (who come from separate eggs and share [[on average half]] their DNA)],) researchers can quantify the extent (to which our genes affect our lives).
句子结构：
*comparing 为动名词，作介词宾语。
* who 为关系代词，引导非限制性定语从句。
* on average half 为介词短语作状语，被移位到宾语之前。
* quantify 为谓语。
* to 开头为定语从句。
*句子主干为researchers can quantify the extent
翻译：另外，通过比较同卵双胞胎和异卵双胞胎的经历，研究人员可以量化我们的基因对我们生活的影响程度，因为后者来自不同的卵子，平均共享一半的DNA。
2.And wherever Bouchard and other scientists looked, <it seemed>, || they found the invisible hand (of genetic influence) helping to shape our lives.
句子结构：
* wherever 为连词，引导状语从句。
* helping 为现在分词，作宾语补足语(即构成复合宾语)。
* to shape 为不定式，作状语。
*句子主干为 they found the invisible hand
翻译：而无论Bouchard和其他科学家在哪里寻找，他们似乎都发现遗传影响的无形之手在帮助塑造我们的生活。
3. These two lines of research-[studying the differences (between identical twins) to pinpoint the influence (of environment), || and comparing identical twins with fraternal ones to measure the role (of inheritance-)] have been crucial [to understanding the interplay (of nature and nurture) [in determining our personalities, behavior, and vulnerability [to disease]].
句子结构：
* study… and comparing…做插入语
* to measure/ to pinpoint为不定式，作状语。
* been 为系动词作谓语，采用现在完成时。
* understanding 为动名词，作介词宾语。
* determining 为动名词，作介词宾语。
* 句子主干为these two lines have been crucial
翻译：
这两条研究路线——研究同卵双胞胎之间的差异以确定环境的影响，以及比较同卵双胞胎和异卵双胞胎以衡量遗传的作用——对于理解自然和培育在决定我们的个性、行为和对疾病的脆弱性方面的相互作用至关重要。
4. These reactions influence | how our genetic code is expressed: how each gene is strengthened or weakened |, [even turned on or off], to build our bones, brains and all the other parts of our bodies.
句子结构：
* how 为连接副词，引导宾语从句。
* even turned on or off 作插入语
* to build 为不定式，作状语。
* 句子主干：these reactions influence
翻译：这些反应影响我们的遗传密码如何表达：每个基因如何被加强或削弱，甚至打开或关闭，以建立我们的骨骼、大脑和我们身体的所有其他部分。
5. One way (the study (of epigenetic) is | revolutionizing our understanding (of biology) is by revealing a mechanism [by {which the environment directly impacts [on genes]}]).
句子结构：
* 第1个 the study 开头为定语从句，引导词 that 被省略。
* revolutionizing 开头为表语从句。
* revealing 为动名词，作介词宾语。
* which 为连接代词，引导宾语从句。
*句子主干：one way is revealing a mechanism
翻译：表观遗传学的研究正在彻底改变我们对生物学的理解，其方式之一是揭示环境直接影响基因的机制。
