题目

假如水稻高秆（D）对矮秆（d）为显性，抗稻瘟病（R）对易感稻瘟病（r）为显性，两对性状独立遗传。现用一个纯合易感稻瘟病的矮秆品种（抗倒伏）与一个纯合抗稻瘟病的高秆品种（易倒伏）杂交，F2中出现既抗倒伏又抗病类型的比例为：A. 1／8 B. 1／16 C. 3／16 D. 3／8 答案：【答案】C【解析】试题根据题意：水稻高秆（D）对矮秆（d）为显性，抗病（R）对易感病（r）为显性，两对性状独立遗传，用一个纯合易感病的矮秆品种（抗倒伏）与一个纯合抗病的高秆品种（易倒伏）杂交，子一代基因型为DdRr，F2中出现既抗倒伏又抗病类型基因型为ddR_，其概率为：×=，C正确，ABD错A: Hello!Welcome to your new school! 51. B: My name is Mary. A：Where are you from?B: 52.         A：How old are you?B: I'm thirteen years old.A：Your English is very good.   Who teaches you English? B: My father. 53.        A: What is your mother's job?B: She is a doctor. By the way (顺便问一下) ，how many students are there in your class? A: There are thirty students in my class. 54.       B; Where is your gym? I want to play table tennis.A: 55.        Please follow (跟随) me!B; Thank you！   A. He is an English teacher in a university in Beijing.   B. Are there any computers on your desks?   C. That's twelve boys and eighteen girls.   D. Can you speak Chinese?   E. What's your name?   F. It's in the white building.   G. I'm fromEngland.