题干

在基因表达载体的构建中,下列说法错误的是(    )

①一个表达载体的必须组成是目的基因、启动子、终止子

②有了启动子才能驱动基因转录出mRNA

③终止子可以终止翻译过程

④不同基因表达载体的构建是不完全相同的

A:②③

B:①④

C:①③

D:③④

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答案(点此获取答案解析)

C

同类题3

    When I was young, my father had one of the first telephones in our neighborhood. I remember the shiny box on the wall. But I was too little to reach it. I could only listen to my mother talk on it.

    I discovered that inside the-wonderful box lived an amazing person whose name was Information Please. There was nothing she did not know.

    One day my mother went out. I accidentally hurt my finger when I was playing with a hammer. I walked around the house sucking my finger, finally seeing the telephone. Quickly I dragged a chair over and climbed up.

    “Information Please, ”I spoke into the receiver. A click or two and a small clear voice spoke into my ear. “Information.”

    “I hurt my finger…”I cried into the phone.

    “Isn't your mother home?” came the question.

    “Nobody's home but me.” I sobbed.

    “Are you bleeding?” the voice asked.

    “No,” I replied, “I hit my finger with the hammer and it hurts.”

    “Can you open your icebox?” she asked. I said I could.

    “Then take a little piece of ice and hold it to your finger.” said the voice.

    After that, I called “Information Please” for everything. I asked her for help with my geography and she told me where Philadelphia was. She helped me with my math. She told me her name was Sally.

    Then, there was the time my pet canary(金丝雀)died. I called “Information Please” and told Sally the sad story. “Why is it that birds sing so beautifully and bring joy to all families, only to end up as a pile of feathers?” She listened, then said quietly, “Paul, always remember that there are other worlds to sing in.” Somehow, I felt better.

    One day when I called “Information Please” again, a different voice answered “Information.”

    I asked for Sally. “Are you a friend?” she said.

    “Yes,” I answered.

    “I'm sorry to have to tell you this,” she said. “She died five days ago.” Before I could hang up she said, “Wait a minute. Did you say your name was Paul?”

    “Yes.”

    “Well, Sally left a message for you. The note said, ‘Tell him I still say there are other worlds to sing in. He'll know what I mean.'” I thanked her and hung up. I knew what Sally meant.