题目

瓢虫的体色黑色(A)对白色(a)为显性,现从一个种群中随机抽取三组,每组100个瓢虫,基因型如下表所示,计算a和A的基因频率分别是( )。 组别AA个体Aa个体aa个体合计 第一组34588100 第二组306010100 第三组266212100 合计9018030300 A.38.5%、61.5%         B.39.5%、60.5% C. 42.0%、58.0%        D.40.0%、60.0% 答案：D 【解析】根据表格分析,三组实验一共统计了300个个体,其中AA 90个,Aa 180个,aa 30个,AA占90÷300=30%,Aa占180÷300=60%,aa占30÷300=10%,因此a的基因频率=aa+(1/2)Aa=10%+(1/2)×60%=40%,A的基因频率=1-40%=60%,故选D项。阅读理解。     In the United States, when you become rich you want people to know about it. And even if you do not become very rich you want people to think that you are. That is what "keeping up with the Joneses" is about. It is the story of someone who tried to look as rich as his neighbors.     The expression was first used in 1913 by a young American called Arthur Momand. He told this story about himself. He began earning $125 a week at the age of 23. That was a lot of money in those days. He got married and moved with his wife to a very wealthy neighborhood outside New York City. When he saw that rich people rode horses, Momand went horseback riding every day. When he saw that rich people had servants, Momand and his wife also hired a servant and gave big parties for their new neighbors.     It was like a race, but one could never finish this race because one was always trying to keep up. The race ended for Momand and his wife when they could no longer pay for their new way of life. They moved back to an apartment in New York City.     Momand looked around him and noticed that many people do things just to keep up with the rich lifestyle of their neighbors. He saw the funny side of it and started to write a series of short stories. He called it "Keeping up with the Joneses" because "Jones" is a very common name in the United States. "Keeping up with the Joneses" came to mean keeping up with the rich lifestyle of the people around you. Momand's series appeared in different newspapers across the country for over 28 years.     People never seemed to get tired of keeping up with the Joneses. And there are "Joneses" in every city of the world. But one must get tired of trying to keep up with the Joneses because no matter what one does, Mr. Jones always seems to be ahead.1. Some people want to keep up with the Joneses because they _______.A. want to be as rich as their neighborsB. want others to know or to think that they are richC. don't want others to know they are richD. want to be happy2. It can be inferred from the story that rich people like to _______.A. live outside New York CityB. live in New York CityC. live in apartmentsD. have many neighbors3. Arthur Momand used the name "Jones" in his series of short stories because "Jones" is _______.A. an important name B. a popular name in the United StatesC. his neighbor's name D. not a good name4. The best title for this passage probably is _______.A. The secret lives of the rich B. How New Yorkers behaveC. Why being rich is never enough D. The funny side of being rich