问题 单项选择题

下列关于反转录的叙述错误的是()

A.反转录是以RNA为模板合成DNA的过程

B.反转录酶是依赖RNA的RNA聚合酶

C.通过反转录可以形成双链DNA分子

D.反转录酶也存在于正常细胞

E.反转录酶属于多功能酶

答案

参考答案:B

解析:反转录是由反转录酶催化的,以RNA为模板合成DNA的过程。反转录酶是依赖RNA的DNA聚合酶,具有多功能性。反转录酶多存在于致癌的RNA病毒,也存在于正常细胞。

单项选择题

Passage Three

If you had asked me then if I would accept a job as a restaurant critic for The New York Times, or any established publication, I would have replied, without a second thought, "Of course not!" And not just because I did not want to think of myself as an ambitious sort. Working in restaurants was honest labor; anyone could see that. Writing about them for the mainstream press was not; it felt like joining the enemy.

But reviewing was fun, so much fun that when mainstream publishers started paying me for my opinions, I didn’t do the decent thing. Before I knew it, I had stopped cooking professionally. Then I stopped cooking altogether. "She’s joined the leisure class," my friends said.

I disarmed my critics by inviting them along; nobody I knew could afford to eat out and nobody refuseD. We went with equal amounts of guilt and pleasure, with a feeling that we were trespassing on the playgrounds of the rich.

We didn’t belong in those starchy restaurants. We always got the worst table. And then, because I didn’t own a credit card, I had to pay in cash. The year turned into two, and three, and more. I got a credit carD. I got good clothes. I was writing for increasingly prestigious publications. Meanwhile, a voice inside me kept whispering, "How could you"

When I receive weekly letters from people who think it is indecent to write about $100 meals while half the world is hungry, the voice yacks right along. "They’re absolutely right," it whispers. And when it asks, "When are you going to grow up and get a real job" it sounds a lot like my mother.

And just about then is when I tell the voice to shut up. Because when my mother starts telling me that all I’m doing with my life is telling rich people where to eat, I realize how much the world has changed.

Yes, there are still restaurants where rich people go to remind themselves that they are different from you and me. But there are fewer and fewer of them. As American food has come of age, American restaurants have changeD. Going out to eat used to be like going to the opera; today, it is more like going the movies.

The word "decent" in "doing the decent thing" in paragraph 2 is closest in meaning to ().

A.very profitable

B.morally acceptable

C.fairly attractive

D.very pleasant

问答题 简答题