问题 单项选择题

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

答案

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。

完形填空
完形填空。
         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
单项选择题