定向进化_爱下问搜题

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问题名词解释

定向进化

答案

参考答案：是指在分子水平上，人为地创造特殊的进化条件，模拟自然进化机制（随机突变、基因重组和自然选择），对酶基因进行改造，并进行定向选择，筛选出所需性质的酶蛋白。

完形填空

阅读下面短文，掌握其大意，然后从36 ~ 55各题所给的四个选项(A、B、C、D)中，选出最佳选项，并在答题纸上将该选项标号涂黑。
It was unusually quiet in the emergency room on December 25. I didn’t think there would be any    , sighing about having to work on Christmas. Just then five bodies       at my desk, a pale woman and four children.
“Are you all       ?” I asked. “Yes,” she said weakly and lowered her head.
But when it came to     of their problems, things got a little strange. They all claimed to have headaches, but the headaches weren’t       by the normal body language of holding the head or trying to keep it still.
Something was wrong. Our hospital policy,       , was not to turn away any patient. I explained it might be a little while       a doctor saw her. She responded immediately, even a bit       “Take your time,” and then added, “It’s warm in here.”
Then, I checked their registration form out of curiosity. No address—they were      .The waiting room was warm. I went back to the nurses’ station and mentioned we had a homeless      in the waiting room. The nurses, complaining of       on Christmas, turned to sympathy for a family just trying to get       on Christmas. The team went into action, much as we do when there’s a       emergency. But this was a Christmas emergency.
We were all       a free meal on Christmas Day, so we took back that meal and prepared a big dinner for our    .We needed presents. We    from different departments candies, fruits and other things     that could be presents. As seriously as we met the      needs of the patients, our team worked to meet the needs of a family who just wanted to be warm on Christmas.
      , as the family walked to the door to leave, the mother came         back, gave me a hug and whispered, “Thanks for being our angels today.”

A．descriptions

C．instructions

A．accompanied

C．acknowledged

B．interrupting

单项选择题

使用糖皮质激素可引起的反应是

A．减少血中中性白细胞数

B．减少血中红细胞数

C．抑制红细胞在骨髓中生成

D．减少血中淋巴细胞数

E．血小板浓度增加