已知控制某遗传病的致病基因位于人类性染色体的同源部分。下图甲表示某家系中该遗传病的发病情况，图乙是对该致病基因的测定，则Ⅱ4的有关基因组成应是乙图中的（）
A.A
B.B
C.C
D.D
参考答案：A
解析：
由Ⅱ3×Ⅱ4→Ⅲ3该病为显性遗传病，又题干中说明致病基因位于人类性染色体的同源部分。Ⅲ3为XaXa，其中一个Xa来自Ⅱ4，Ⅱ4是患者，另一个Y上只能是YA，所以，Ⅱ4的基因型是XaYA，Y染色体较短，A项正确。
考点：本题考查伴性遗传，意在考查考生能运用所学知识与观点，通过比较、分析与综合等方法对某些生物学问题进行解释、推理，做出合理的判断或得出正确的结论。
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| Mr. Green was ill and went to the hospital. A doctor 1 and said, "Well, Mr. Green, you are going to 2 some injections (注射), and you'll feel much better. A nurse will come 3 give you the first one this evening, and then you'll 4 get another one tomorrow evening." 5 a young nurse came to Mr. Green's bed and said to him, "I am going to give you your 6 injection now, Mr. Green. Where do you want it?" The old man was 7 . He looked at the nurse for a 8 , then he said," 9 has ever let me choose that before. Are you really going to let me choose now?" "Yes, Mr. Green," the nurse answered. She was in a hurry. "Where do you want it?" "Well, then," the old man answered 10 "I want it in your left arm, please." |
| ( )1. A. looked for him ( )2. A. get ( )3. A. so ( )4.A. must ( )5. A. In the morning ( )6. A. first ( )7. A. confident ( )8. A. hour ( )9. A. Somebody ( )10. A. with a smile | B. looked him over B. give B. but B. can B. In the afternoon B. one B. surprised B. minutes B. Anybody B. in time | C. looked after him C. make C. or C. had better C. In the end C. two C. full C. year C. Nobody C. in surprise | D. looked him up D. hold D. and D. have to D. In the evening D. second D. hungry D. moment D. people D. with tears in his eyes |