现在医学科学工作者通过获得大量特异 DNA，结合适当的分析技术_爱下问搜题

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问题单项选择题

现在医学科学工作者通过获得大量特异 DNA，结合适当的分析技术即可鉴定基因缺陷。当前临床或研究室获得大量特异 DNA片段最流行的方法是( )。

A．化学合成

B．DNA合成仪合成

C．从外周血细胞大量制备

D．基因克隆

E．聚合酶链反应

答案

参考答案：E

解析：聚合酶链反应技术(PCR)是利用人工合成的核苷酸序列作为“引物”，在耐热DNA聚合酶的作用下，通过变化反应温度，扩增目的基因，用于检测体液，组织中相应核酸的存在，在扩增循环中DNA片段上百万倍增加是很特异和非常灵敏的方法。

完形填空

Do you know who invented tea? It is said that the emperor Shen Nong  discovered   tea when he was boiling drinking water 21 an open fire. Some leaves from a nearby tree fell into the water and the leaves were in the water for  22 . The emperor noticed that the leaves in the water produced a  23   smell. Later he decided 24 the hot water with the leaves. It was quite delicious. And  25 , one of the worl’s favorite drinks was invented.
26 is the home of tea. And tea has more than 4,000 years history. 27  the three drinks—tea, coffee and cocoa, tea is drunk by  28  people in the world. Tea 29 China began to be known by the world over a thousand years ago and has been an important Chinese export (出口商品) 30 .
Tea leaves  31  mainly in the south of the Yangtze River, 32 the warm climate (气候)there. Longjing, Wulong, Pu’er and Tieguanyin are all  33   kinds of tea.
Over the past centuries, Chinese people  34   their tea culture(文化), including tea planting, tea-leaf picking, tea making and so on. We know tea is  35   a popular topic(主题) in dances, songs, poems and novels.

A．not to taste

D．in this way

A．the number of	B．a number of
C．a large number of	D．the largest number of

A．At that time

B．from now on

B．are produced

A．becauuse of

A．interesting

A．had developed

B．have developed

D．are developing

多项选择题

房地产品具有（）的特点。

A.产品区位的固定性

B.产品使用的长期性

C.房地产品的单件性

D.房地产品规模大价格昂贵

E.房地产品使用上的限制性