云南农业大学英语四第一次作业.docVIP

云南农业大学英语四第一次作业 （课程代码3061050） 阅读理解Directions:In this section there are some passages. Each passage is followed by some questions or unfinished statements with four choices marked A), B), C), and D). You are supposed to read the passage and make the best choice to complete each question or unfinished statement. Then type the answer in the blank on the web page.[题数:25;分数:100分;参考时间:50分0秒]Passage 1 Some 200,000 babies are born in the United States each year with deformed bodies, impaired minds and possibly fatal abnormalities in body chemistry often because of defective genes or chromosomes. If a way could be found to test routinely the genes of prospective married couples-much as the couples now take Wassermann tests to detect syphilis(梅毒 )-the toll(伤亡人数) might be reduced drastically. This is the goal of genetic counseling. And while it is still far off--testing is expensive and elaborate--genetic counseling centers in hospitals and clinics across the United States are already helping parents. At a symposium sponsored by the National Foundation March of Dimes in New York City, it was announced that between 1955 and 1969 the number of centers bad grown from 20 to 114. Such centers help the parents of a defective child in their couples with family histories of genetic diseases even before marriage.The genes that help determine a persons individual characteristics-from the colors of his eyes to the score he makes on an IQ test-are located on chromosomes within the cells of his body. Half of a persons chromosomes come from his father, half from his mother. Many diseases are the result of a single defective gene on one of the chromosomes. Achondroplastic(软骨营养障碍性) dwarfism, for example, is caused by a dominant gene and any child who inherits it will have the disease. A genetic counselor confronted by a parent with such a disease could warn that half of his children risk the disease.More often, genetic disease are caused by recessive genes(隐性基因). The most common is cystic