问题
单项选择题 A1/A2型题
体外扩增DNA或RNA的步骤是（）。
A.延伸-变性-退火
B.变性-退火-延伸
C.变性-延伸-退火
D.延伸-退火-变性
E.退火-延伸-变性
答案
参考答案：B
解析：PCR循环有三个阶段，即变性-退火-延伸。
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体外扩增DNA或RNA的步骤是（）。
A.延伸-变性-退火
B.变性-退火-延伸
C.变性-延伸-退火
D.延伸-退火-变性
E.退火-延伸-变性
参考答案：B
解析：PCR循环有三个阶段，即变性-退火-延伸。
| 从方框中选择最佳选项补全对话，其中有两项是多余的。 | |
R: Hello. Susan 1 S: I'm with a team of explorers (考察者) and scientists. We're having a trip to the North Pole (北极圈). R: 2 S: On foot. R: 3 S: It's a long way. We're walking over 1,000 kilometers! R: 4 S: It's very, very cold. During the day it's often sunny and windy, too. R: 5 S: Well, we're all wearing very warm clothes, so it's OK. R: Of course, there aren't any hotels in the North Pole. Where do you sleep? S: We've got special tents and sleeping bags. The temperature is—35C at night. R: Oh, it's awful! Thank you, Susan. Goodbye. S: Goodbye. 1._____ 2._____ 3._____ 4._____ 5._____ |
