题干

某研究人员模拟赫尔希和蔡斯关于噬菌体侵入细菌实验,进行了以下4个实验:
①用未标记的噬菌体侵染35S标记的细菌   ②用32P标记的噬菌体侵染未标记的细菌
③用未标记的噬菌体侵染3H标记的细菌   ④用15N标记的噬菌体侵染未标记的细菌
以上4个实验,经过一段时间后离心,检测到放射性主要部位是

A:沉淀、沉淀、沉淀和上清液、沉淀和上清液

B:沉淀、上清液、沉淀、沉淀和上清液

C:上清液、上清液、沉淀和上清液、上清液

D:沉淀、沉淀、沉淀、沉淀和上清液

上一题 下一题 0.0难度 选择题 更新时间:2018-06-09 03:02:28

答案(点此获取答案解析)

D

同类题4

阅读理解

    Anki has introduced Cozmo, a little robot powered by an advanced artificial intelligence. Cozmo promises to be for more interactive(互动的)than any toy robot.

    Cozmo, which can lie in your hand, has a “brain”---technically its CPU---that can process data amazingly fast. In addition, Cozmo has a playful personality. He's designed to react to emotions and even ask users to play with him.

    Cozmo is not the first interactive toy to reach the market nor is it the first robot toy. What sets Cozmo apart from the other “smart toys” is that it has greater play value than those toys, which can become repetitious all too quickly.

    “Every interaction with Cozmo is different, so you do not put up with repetitive play patterns and responses typically found with other preprogrammed robots,” explained Anki spokesperson Peter Nguyen. Because it has functionality that is similar to that of video games, Cozmo also can receive regular updates, which could extend its playability. Still, Anki has designed this toy to be just that: a toy. It's not an advanced computerized robot. Its software is app-based.

    Cozmo lacks the “traditional” human-like robot form factor(要素)of legs, arms, and a head. But Cozmo does have an OLED screen/face with blue eyes, which in fact were designed to help it connect with its user.

    “I'm glad my kids are already raised,” said Roger L. Kay, analyst at Endpoint Technologies Associates. “Otherwise, they might become more antisocial if their relationship with Cozmo is more satisfying than those with real people,” said Kay. “Cozmo might encourage kids to learn more about technology or even inspire them to try programming and similar studies,” said Charles King, analyst at Pund-IT.

    Yet this technology does promise to be more than a toy. “It's a pretty cool invention and might have further applications, for example in elder care,” suggested Kay.