题干

下面是某同学在使用同位素标记法的实验中遇到的一些问题,其中正确的操作或结论是(    )

A:给豚鼠的胰腺腺泡细胞注射用3H标记的核苷酸,一段时间后,可依次在核糖体、内质网和高尔基体中检测到放射性

B:小白鼠吸入18O2,则其尿液中可以检测到H218O

C:在探究光合作用释放O2中氧的来源实验中,可用18O同时标记H2O和CO2作为小球藻光合作用的原料

D:用15N标记精原细胞的DNA双链,然后放在含14N的培养基中,进行减数分裂产生的4个精细胞中,含15N的精细胞所占的比例是50%

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答案(点此获取答案解析)

B

同类题5

A栏是五项有礼貌的请求或建议,B栏是七项应答.请将它们匹配起来,并将答案的字母编号填写在题前的括号内。

    A

    B

(1)Hi, Nancy. Could you please wash the dishes after dinner?____ 

(2)Mum, could I go to the movies with my cousin Sally and Cindy? I have not seen a movie for long.____ 

(3)Is this your dog, sir? This is a dangerous dog. It may hurt others. Please, keep it at home and take good care of it.____ 

(4)Weekend is coming. Are you free then, Mr. Green? Could you go fishing with us?____ 

(5)I just cut my left finger. Blood is running down. Could you drive me to the hospital to see the doctor, Mr. Green?____ 

A. Sure, that should be OK. But you must be careful on the way because there is so much ice and snow on the road. And go back home soon after the movie.

B. Of course. I am glad to help you with the housework and cooking. Then we can have a big dinner together.

C. I'd love to. But I have to stay at home and look after my sister. My parents are both at work. Fishing is really fun. I am sure to go with you next weekend.

D. Sorry, I am afraid I can't go to your party on Saturday. My uncle is coming to see me that day. I have to pick him up at tile airport and show him around my hometown.

E. OK, Dad. We don't have many dishes to wash today. It can only take me about five minutes to wash them.

F. Let me see. It's really a deep cut. Let's go to the hospital quickly. I am afraid the doctor may operate on your finger.

G. Thanks for telling. My dog once got a special training. In fact, it is friendly. It won't attack  people unless he is attacked.