托福阅读实练与讲解

Until only just few centuries ago, people believed that the genes of the parent and the child blended together and constituted the exactly same genetic makeup. Then in the early 1800s, Gregor Mendel, renowned Austrian scientist,discovered that only certain traits such as the shape of the nose, eye color etc.,were passed from parent to child. As a result of his work, and the work of many scientists since, we now know that many of our physical and behavioral characteristics are determined by factors called genes that is to say that genetic factors handed down from our parents. We also know that our genes as well as our lifestyles contribute to many common diseases.

 

 

The genes we inherit from our parents program our development from conception to adulthood. In each cell we have about 90,000 pairs of genes arranged on 23 pairs of chromosomes; one of the pair being maternal and the other being paternal. Although our brothers and sisters inherit genes from the same parents the mixture of genes is slightly different in each sibling. It is the reason every organism is different.

 

 

Each gene provides instructions for a cell to carry out a single chemical process; they also control the growth and reproduction of cells. They are responsible for the development of the embryo, first into a baby, then a child and eventually an adult. Throughout our lives, genes control cell functions and the repair and replacement of dead or damaged cells. Blood relatives have many genes in common and these genes help to determine family physical characteristics and other traits. Most of these traits, such as the shape of the nose are trivial and have no significant effect on health. Other traits, such as being abnormally short or tall or having a tendency to be overweight , can be associate with an increased risk of certain diseases.

 

 

Some diseases such as hemophilia and cystic fibrosis are directly caused by a fault or mutation in a single gene or pair of genes. These rare diseases follow a predictable pattern of inheritance, and this means that families in which the gen is present can usually be given clear, reliable information regarding the risk of the disease affecting future generations. Therefore, gene therapy holds great promise for the cure of diseases and researchers will sooner or later come up with a way to lix the abnormal genes that make us sick without disrupting the normal ones.Viruses, as a way to cure certain diseases, however, replicate easily and move around in the body and interact with other genes, so a virus that is used to cure hemophilia can replicate and enter an area where a tumor gene is located and stimulate it to cause a cancer. In case DNA from bacterium is used, the story might be different though.

 

 

More common than these genetic disorders are those in which genes, along with other factors, contribute to a family's susceptibility to certain diseases. For example, some disorders, such as coronary artery disease, tend to run in families, but lifestyle factors such as a high-fat diet, smoking, and lack of exercise also play a part in determining whether these diseases develop. In some diseases that have a genetic component, including asthma, environmental factors, such as living in a polluted area, also play a crucial role. Cancer is not caused simply by one gene,but rather it is a result of a whole variety of circumstances. In a lab, mice were genetically altered to include a gene that causes tumors in the retina of the eye in humans, but surprisingly, none of them developed any symptoms of this disorder.Such complex interplay between genetic susceptibility and environment makes it difficult to predict the risks in adult life for children who are born into families affected by disorders of this kind.

 

 

We are now aware of the fact that we are susceptible to diseases passed through families and that our lifestyles can serve to exacerbate symptoms and the early onset of a disease such as heart disease. The good news is that we can use this information to arm ourselves against diseases brought on by an unhealthy lifestyle. If we know that our genes carry a likelihood that we might develop heart disease then it would be prudent to try to live a healthy lifestyle.

 

 

Question 1:

Based on the information in paragraph 3, what can be inferred about family traits?

A A tendency toward obesity can often spark the onset of many other diseases.

B If one's parents are overweight then it follows that their children will also be overweight.

C Siblings carry the same genes and so always have the same genetic characteristics.

D Usually, we only inherit positive genetic characteristics from our parents.

 

Question 2:

According to paragraph 4, what can be inferred about people who can be given reliable information?

A Doctors can assess how big a risk a child might face of inheriting a genetic disease.

B The mother can choose whether or not to abort the child based on the information given by the doctor

Doctors can assess if parents can pass on a rare genetic mutation based on the chromosomes

D The doctor can advise a couple whether or not it is advisable to have children considering the risks.

 

Question 3:

Based on the information in paragraph 5, what can be inferred about the genetic and lifestyle factors explained in paragraph one?

A Certain diseases are passed from generation to generation and can be made worse by an unhealthy lifestyl

B People who have asthma should in no circumstances live in heavily polluted areas such as cities.

C The negative gene causing coronary disease is always passed on in families.

D Sometimes negative genes that skip generations are passed further along the line.

 

Question 4:

According to paragraph 5, disease-causing genes are inherited but what does paragraph 2infer about the possibility of two sisters inheriting a gene causing coronary disease?

A It is most likely that the two sisters will carry the same negative gene and suffer from the disease.

B Siblings do not inherit the exactly same shuffle of genes so it doesn't always follow that they will inherit the same negative genes.

C Brothers inherit the same shuffle of genes, as do sisters, so they will inherit the same negative genes.

D All genetic diseases follow a predictable pattern in siblings and in future generations.

 

Question 5:

According to the passage, what can be inferred about DNA from bacterium?

A Using it might have less side-effect than viruses.

B It stimulates a tumor gene to cause a cancer.

It will be more effective to cure a cancer than viruses.

D There aren't big differences between DNA from bacterium and viruses.

 

Question6:

According to the passage, what can be inferred through the mice experiment?

A It is not desirable as a way of genetic experiments.

B The results of some experiments are sometimes different from what people expect.

C It is found that cancer is a result of a variety of reasons

D Tumors of the retina of the eye in humans are also developed in the mice.

 

Question 7:

Based on paragraph 6, what can be inferred?

A An individual should inform the doctor of any symptoms.

B An individual should exercise and eat well to avoid early onset of an inherited disease.

C An individual should go for regular tests.

D Everyone should avoid any activity that might cause strain to the heart.

 

参考译文

 

几个世纪之前，人们还一直以为父母和子女的基因混合在一起会构成完全相同的基因结构。直到19世纪早期，澳大利亚的著名科学家格利高利·孟德尔发现只有某些特征，诸如鼻子的外形，眼睛的颜色等是由父母遗传给子女的。由于他和此后许多科学家们的研究，我们今天知道，我们许多身体上、行为上的特征是由基因（父母遗传给我们的遗传物质）决定的。我们还得知，基因和生活方式导致了许多常见的疾病。

 

从父母那里遗传的基因决定了我们从胎儿时期到成人时期的发育。每个细胞内有由23对的染色体排列的9万多对基因。每一对中，有一条来自母方，一条来自父方。尽管我们的兄弟姐妹继承了相同父母的基因，但每个人的基因的组合是不一样的，因此每一个有机体都是不同的。

 

每个基因指示每个细胞进行独立的化学作用。他们还控制细胞的生长和繁殖，这就是从胎儿到婴儿，从婴儿到儿童，从儿童到成人，这样成长的原因。在我们一生当中，基因控制细胞的功能，还能修复损伤的细胞或者替换死亡的细胞。有血缘关系的亲戚有很多相同的基因，这些基因帮助决定一个家族的身体特征和其他特征。大多数的特征是不太显著的（如鼻子的外形）,而且不会对身体有重要影响。其他一些特征，如过矮、过高或有超重趋势则与患某些疾病危险性的增加息息相关。

 

血友病和囊肿性纤维化等特定的疾病是由一个基因或者一对基因的错误或突变引起。这些罕见的疾病遵循着可以预测的遗传模式，这就意味着我们通常可以为有这种基因的家族提供这些疾病对其后代可能造成的危险性的明确可靠的信息。因此，基因疗法使疾病有望根治，研究者们迟早会找出办法在不影响正常基因前提下修补使我们患病的非正常基因。但是，用于治疗特定疾病的病毒很容易被复制，而且在身体内部来回移动并与其他的基因相互作用。因此，为了治疗血友病而使用的病毒可以复制并进入到有肿瘤基因的区域，从而会刺激基因导致癌症。不过一旦细菌中的DNA开始使用，情况就大不相同了。

 

比基因变异更常见的是基因与其他因素一起导致某个家族更易患某种疾病。例如，某些疾病，如冠心病等，很容易在家族内部流传，而高脂肪的饮食、吸烟、缺乏运动等生活方式在某种程度上也决定发病与否。对于哮喘等有遗传因素的疾病，环境因素（如生活在严重污染地区）也是个至关重要的因素。癌症不是由一种基因引起的，而是多种情况共同导致的结果。在实验室给老鼠注入了引起人类视网膜肿瘤的基因，但令人惊奇的是任何老鼠都没有出现这种疾病的症状。基因感染的可能性和环境之间如此复杂的相互作用，使我们很难预测在有某种病变的家族出生的小孩，成年时得这种疾病的可能性。

 

现在，我们都认识到：我们易患家族遗传的疾病，我们的生活方式会加剧心脏病等疾病的症状，并导致其提前发作。但有利的是，我们可以利用这些信息来保护自己，避免不健康的生活方式所引起的疾病。如果知道了自己的基因具有患心脏病的可能性，我们就会谨慎地选择健康的生活方式。

 

词汇

blend混合 m constitute 构成 a genetic 造传性的 makeup构成 a trait特性

pass传透predictable way可预测的方式"physical身体上的behavioral行动上的 factor要素 a contribute to 贡献inherit 继承，遗传 m conception 胎儿 adulthood成人期 m chromosome 染色体 maternal 母亲的 paternal 父亲的 mixture混合 slightly很少 sibling 兄弟姐妹  instruction 指示 growth成长

reproduction 紧殖 embryo胎儿 eventually结果 adult成人 replacement 替换 damaged 破损的 characteristics 特性 trivial 琐碎的 significant 重大的hemophilia 血友病 cystic fibrosis 食肿性纤维化 mutation 突变  rare 稀奇的inheritance遗传come up with提出 abnormal 非正常的  disrupt中断 replicate复制

Susceptibility容易感染的可能性 along with与…一起 run蔓廷develop感染

a component成分 asthma哮喷 =】polluted污染的crucial重要的，有决定性的

variety多样性  circumstance环境 a genetically 违传地 alter变化  retina视同膜symptom 症状  

complex复杂的  disorder疾病  exacerbate 恶化  onset开始 likelihood可能性

 

问题1:

 

根据第三段的信息，关于家族的特性能推断出的是：

 

A肥胖可导致很多疾病的发生。

B一个人的父母超重的话，那么这个孩子也会超重。

C因兄弟姐妹有同样的基因，所以也有同样的遗传特性

D一般我们只继承父母的好的遗传特征。

 

解析：

第三段的句末写道“Other traits,such as being abnormally short or tall or having a tendency to be overweight , of can be associated with an increased risk of certain diseases, 因此超重也可以导致疾病答案：A

 

问题2:

 

根据第四段，对于人们能得到可靠信息，可以推论出什么？

 

A医生可以估计孩子继承遗传病的可能性大小

B母亲根据医生提供的情况可以决定是否堕胎。

C医生根据染色体可以判断出父母有没有可能把罕见的染色体突变的基因遗传给后代。

D医生考虑到危险，可以给夫妇是否生孩子提供适当的建议。

 

解析：第四段写道“These rare diseases follow a predictable pattern of inheritance,and this means that families in which the gene is present can usually be given clear, reliable information regarding the risk of the disease affecting future generations",即能获取影响下一代的疾病的危险性的数据。

答案：A

 

问题3:

 

根据第五段的信息，可以推论出第一段说明的遗传因素和生活方式因素的哪些方面？

 

A特定的疾病会代代相传，但不健康的生活方式也会导致疾病的恶化。

B得哮喘的人们不应该生活在像城市这样的污染严重的地区。

C导致冠心病的不好的基因永远在家族内部遗传。

D有时候不好的基因跨越数代还会再次遗传。

 

解析：第五段的第一个句子里表明“genes,along with other factors,contribute to a family's susceptibility to certain diseases",因此遗传因素与环境因素共同导致了疾病。

答案：A

 

问题4:

 

第五段表明引起疾病的基因是可以遗传的，对于两姐妹遗传到冠心病基因的可能性由第二段可以推论出的是：

 

A两个姐妹将拥有同样不好的基因，得疾病的可能性很高

B兄弟姐妹没有继承完全相同的混合基因，所以不会总是继承同样不好的基因。

C姐妹和兄弟都会继承同样的混合基因，所以也会继承同样不好的基因。

D所有的遗传疾病对姐妹和后代的影响是可以预测的。

 

解析：第二段写道，"The mixture of genes is slightly different in each sibling"。

答案：B

 

问题5:

 

根据文意，从有关细菌抽出的DNA可以推论出什么信息？

A利用这个比直接利用病毒副作用会少点。

B刺激肿瘤基因，导致癌症的发生

C比病毒更能有效的治疗癌症。

D从细菌抽出的DNA与病毒之间没有太大的差别。

 

解析：第四段提出了治疗疾病的病毒的缺点，并写道“In case DNA from bacterium is used,the story might be different though",因此可以得知利用DNA比利用病毒缺点少。

答案：A

 

问题6:

 

根据文意，通过小老鼠实验我们可以推论出的是：

 

A作为基因实验的一个方式不是很理想。

B有的实验结果与人们的想象不一样。

C癌症是很多因素综合作用的结果。

D人类眼睛的视网膜肿瘤也出现在小老鼠身上。

 

解析：

说明老鼠实验的时候写道“But surprisingly,none of them developed any symptoms of this disorder"、因此可以得知实验结果与想象中的不一样。

答案：B

 

问题7:

 

根据第六段可以推论出的是：

 

A 一个人应该把所有的症状都告诉医生。

B为了防止遗传病的发作，一个人应该经常锻炼，注意饮食。

C一个人应该定期进行检查。

D每个人都应该避开一切给心脏带来负担的活动。

 

解析：

最后一段的第一句写道“Our lifestyles can serve to exacerbate symptoms and the early onset of a disease such as heart disease",因此可以得知、改善生活方式会避免疾病的发生。

答案：B