题目

下列对噬菌体侵染细菌实验的分析，错误的是A. 染色体变异不能发生在噬菌体中B. 离心的目的是让上清液中析出重量较轻的噬菌体，沉淀物中留下大肠杆菌C. 离心后上清液放射性高、而沉淀物放射性低，则亲代噬菌体应是用35S标记的D. 噬菌体蛋白质是否进入大肠杆菌，可用32P标记的实验组确定 答案：【答案】D【解析】噬菌体属于病毒，没有细胞结构，也就没有染色体，所以不能发生染色体变异，A项正确；离心的目的是让上清液中析出重量较轻的T2噬菌体颗粒，沉淀物中留下被感染的大肠杆菌，B项正确；35S标记亲代噬菌体的蛋白质外壳，由于噬菌体侵染细菌时，蛋白质外壳留在外面，所以离心后Sandy is still puzzled about the meanings of some words. Help her match the words with their meanings. 1. shortly_____a.  more than sth 2. lifetime_____b.  a thing that sb has done successfully 3.well-known_____c.  (of people)not having enough money, food, etc. 4.achievement_____d.  to give sth to sb, for example, at a formal or official occasion 5 .needy_____e.  to give most of your time, energy, attention etc. to sb/sth 6.devote_____f.  known about by a lot of people 7.beyond_____g.  not long; soon 8.present_____h.  the length of time that sb lives or sth lasts