Question

Every living cell contains genes. They are too small to be seen in a microscope, but they are very important. Each set of genes in the body contains all the instructions needed to make a human being. Some genes determine hair color. Some determine the shape of a nose. Some genes help determine your height and even your weight.

Genes are made of a chemical called DNA-the letters stand for deoxyribonucleic acid(脫氧核糖核酸). In the early 1950's, two scientists, Francis Crick and James Watson, figured out how the parts of DNA fit together. Once scientists understood this structure, it became possible to take pieces of DNA apart and put them together in new ways. New kinds of genes could be made in this manner.

Scientists have studied the genes of many plants and animals. They have worked out which genes affect the color of a tomato and the thickness of its skin. Working out which genes determine which features is called genetic mapping, scientists have begun the Human Genome Project, an ambitious effort to map all the genes in the human body.

Some genes may be defective(有缺陷的). For example, something might be wrong with the gene that makes blood clot(凝聚). A baby born with this defective gene could suffer serious hemorrhages(出血) or even bleed to death because his or her blood fails to clot. If scientists ever learn how to map all the genes in our bodies, they can determine whether or not an unborn child has any defective genes. They might even discover how to treat these genes before the child is born.

1.What was the achievement of Francis Crick and James Watson?

A. They discovered why people have different hair colors.

B. They learned that some people bleed for long periods of time.

C. They looked at human cells under the microscope.

D. They worked out the structure of DNA.

2.What is the main idea of this passage?

A. Defective genes can never be repaired.

B. Genes are too small to be seen through a microscope.

C. Genes help scientists understand how living things develop their characteristics.

D. The Human Genome Project may explain the role of every gene in the body.

Answer 1

1.D

2.C

【解析】

試題分析：每一個活的細(xì)胞都含有基因，它們雖然很小，但卻非常重要�；�因是帶有遺傳信息的DNA片段，DNA是脫氧核糖核酸的縮寫。一些基因決定頭發(fā)的顏色，一些決定鼻子的形狀，一些決定一個人的身高甚至體重。

1.two scientists, Francis Crick and James Watson, figured out how the parts of DNA fit together”可知，F(xiàn)rancis Crick和James Watson弄清楚了DNA的結(jié)構(gòu)，故選D。

2.Each set of genes in the body contains all the instructions needed to make a human being. Some genes determine hair color. Some determine the shape of a nose. Some genes help determine your height and even your weight.”可知，文章主要講的是基因能夠幫助科學(xué)家了解生物的性格特征是怎樣發(fā)展的，故選C。

考點：科學(xué)類短文閱讀