问题
选择题
亚硝酸盐可使DNA的某些碱基中的氨基脱去，碱基脱去氨基后的变化如下：C转变为U（U与A配对），A转变为I（I为次黄嘌呤，与C配对）。现有一DNA片段为
，经亚硝酸盐作用后，若链①中的A、C发生脱氨基作用，经过两轮复制后其子代DNA片断之一为 [ ]
A．
B．
C．
D．
答案
答案：C
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亚硝酸盐可使DNA的某些碱基中的氨基脱去，碱基脱去氨基后的变化如下：C转变为U（U与A配对），A转变为I（I为次黄嘌呤，与C配对）。现有一DNA片段为，经亚硝酸盐作用后，若链①中的A、C发生脱氨基作用，经过两轮复制后其子代DNA片断之一为 [ ]
A．
B．
C．
D．
答案：C
| 根据语篇内容，用方框中所给词的正确形式填空，使短文通顺、连贯。方框中有两个词为多余项。 | |
1______. Through the window, I could often see a woman 2______ I had never met doing some reading in the house every afternoon. Several 3______went by, I began to notice that her window was dirty. Everything was not very clear through the dirty window. 1 wondered why the woman didn't wash her window, it 4______ looked terrible. One bright morning, I decided to clean my house, including 5______ the window inside. Late in the afternoon when I finished all the cleaning, I sat down by the window with a cup of coffee for a rest. How 6______! I found that the woman's window was actually so clean that she could 7______ clearly sitting by the window. That was quite an 8______ lesson for me. How often had I looked at others through my own shortcomings (缺点)! Since then, I 9______ used to asking myself whether I am looking through my own dirty window. Before I want to judge (判断) someone, I always think 10______ than before and try to clean the dirty window so that I may see the world around me more clearly. |