题目

如图为DNA分子的某一片段,其中①、②、③分别表示某种酶的作用部位,则相应的酶依次是(  )                                                  A.解旋酶、限制酶、DNA聚合酶                   B.DNA酶、解旋酶、DNA连接酶         C.解旋酶、限制酶、DNA连接酶                   D.限制酶、DNA连接酶、解旋酶          答案:解:①为氢键,是解旋酶的作用位点;                                                     ②为磷酸二酯键,是限制酶的作用位点;                                                 ③是DNA连接酶、DNA聚合酶的作用位点,能连接形成磷酸二酯键.                  故选:C.                                                                                         
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