题目

某种植物果实重量由三对等位基因控制，这三对基因分别位于三对同源染色体上，对果实重量的增加效应相同且具叠加性。已知隐性纯合子和显性纯合子果实重量分别为150g和270g。现将三对基因均杂合的两植株杂交，F1 中重量为190g的果实所占比例为（ ）A. 3 / 64 B. 5 / 64 C. 12 / 64 D. 15 / 64 答案：【答案】D【解析】由于隐形纯合子的果实重量为150g，而显性纯合子的果实重量为270g，三对等位基因中每个显性基因增重为（270—150）÷6=20（g），因此三对基因均杂合的两植株杂交，F1中重量为190g的果实的基因型中含有显性基因个数为：（190—150）÷20=2，若用A和a、B和b、C和c这三对等位基因来表示，重Betty is an English girl. She studies in a middle school. On weekdays(非休息日) she gets up at 6:30. She has breakfast at seven. Then she goes to school on her bike(自行车). The school is near her home. She gets to school at around seven-thirty. Classes start at eight o’clock. She has four classes in the morning and two in the afternoon. Her favorite subject is history. She has lunch at 12:00 at school. Classes end(结束) at three-thirty. After school she usually goes to the history club and then goes home. She gets home at 5:00.1.How does Betty go to school?A. She takes a bus.B. She goes on her bike.C. She runs to school.2.What time does she get to school?A. At around eight.B. At around seven-thirty.C. At around eight-thirty.3.How many classes does she have every day?A. Four. B. Two. C. Six.4.Where does she have lunch?A. At school.B. In a restaurant(饭店).C. At home.5.What does she do after school?A. She plays sports.B. She does homework.C. She goes to the history club.