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问题 选择题

镰刀型细胞贫血症的病因是血红蛋白基因的碱基序列发生了改变。检测这种碱基序列必须使用的酶是[ ]

A．解旋酶

B．DNA连接酶

C．限制性内切酶

D．RNA聚合酶

答案

答案：C

默写题

积累资料。    

     《闻官军收河南河北》和《示儿》都表现了诗人热爱祖国的情怀。你还知道哪些古诗也表达这样的情感吗？选二首写出来。

                                                                                                                                                          

                                                                                                                                                          
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选择题

Germs are very small. They can ______ the human body ______ the skin. [ ]

A. get up…across

B. get into…through

C. get out of…from

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