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