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问题 单项选择题

下列对逆转录的叙述错误的是

A．以RNA为模板合成双链DNA

B．逆转录的合成原料为4种dNTP

C．逆转录与转录相似，均不需要引物

D．RNA:DNA杂化双链为过程的中间产物

E．逆转录酶可催化模板RNA水解

答案

参考答案：C

解析：[考点] 逆转录及逆转录酶[分析] 逆转录也称反转录，是依赖RNA的DNA合成过程，以RNA为模板，以4种 dNTP为原料合成双链DNA分子，合成反应也是从5'向3'延伸新链，合成过程中是需要引物的，现在认为其引物是病毒本身的一种 tRNA，这是与转录不同的。在反应过程中以 RNA为模板先合成一条单链DNA，这样模板与产物形成RNA:DNA杂化双链，这只是个中间产物，此后逆转录酶(RNA酶活性部分)催化RNA水解，余下产物单股DNA链，最后逆转录酶(DNA聚合酶活性部分)再催化DNA合成。

阅读理解

阅读下面的短文，并根据短文后的要求答题。

     Dragon-boat Festival (端午节) Dragon-boat Festival also called the Duanwu Festival, is celebrated on the

fifth day of the fifth month according to the Chinese calendar. For thousands of years, the festival has been

marked by eating Zong Zi and racing dragon boats. To hold the dragon-boat races is in memory of Qu Yuan, one

of the greatest poets (诗人) in China. 

     QU Yuan was born in Zigui of Hubei Province over 2,200 years ago. Qu Yuan was an honest minister (大臣)

of the State of Chu, during the Warring States Period (475-221BC) (战国时期). He was upright and wise. He

wanted to bring his country peace and make the State more stronger, but the country was in the hands of bad of

ficials, he failed. At last, he was very discouraged. (1) the Miluo River, throwing, he, into, himself, life, by, his,

ended. (2) 据说当时人们从船上跳下去试图救他。But it was too late. Also, they were very sad and they threw

rice into the water to feed Qu Yuan's spirit.

     (3) Now we read his poem Li Sao which was filled with deep love for his country. We can see the

dragon-boat races and have a kind of Chinese food named Zong Zi to eat during the Dragon-boat Festival.

1．What are the two important things on the Dragon-boat Festival?

                                                                                                    

2．把(1)划线部分的单词组成句子。

                                                                                                    

3．将文中(2)处的汉语句子译成英语。

                                                                                                    

4．把文中(3)处的划线部分译成汉语。

                                                                                                    

5．List the words that can describe the qualities (品质) of Qu Yuan. (at least 3) 

                                                                                                      

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单项选择题

以下程序的运行结果是 ( )
　　# include＜stdio．h＞
　　main( )
　　　int a＝015，b＝22；
　　　printf("%d，%d\n"，a+ +，- -b)；

A．15，22

B．15，21

C．13，21

D．14，21
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