题干

下列说法错误的是( )

A:子代噬菌体外壳在噬菌体DNA指导下,用细菌物质合成

B:用15N标记的DNA分子不论复制几次,含15N的DNA分子只有两个

C:转录和翻译碱基配对方式不相同,所需原料也不同

D:反密码子为CAU的tRNA转运的氨基酸对应的密码子为GTA来源:Z.xx.k.Com

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答案(点此获取答案解析)

D

同类题2

   Recent research from the Pew Internet Project suggests that 90% of Americans aged from 12 to 17 use the Internet, and 51% of those teens use social networks. However, there are many possible problems with social networking sites and the teenagers who use them.

   Apart from the social advantages, social networking sites can be used to record school research, develop artistic talents and experiment with other forms of subject creation. They provide a way to communicate with others who share the same interests and to get helpful advice on ongoing projects.
   Along with these advantages come some dangers. For example, most social networking sites are open to all, especially MySpace, which is the most popular social network among teens in America. It means that they could be put in unpleasant and frightening situations.
A greater danger is that teens may become objects of the people with secret purposes. The secrecy of some social networking sites makes it easy for dangerous people to find young teens and invite them into dangerous conversations. It’s easy for them to pretend as teens and draw children into dangerous real-world communication as well. Then further hurt might be on its way.
   Another danger is identity stealing, which can happen when teens share too much information about their names, dates of birth and locations.
   Therefore, it's very important to make sure teens are safe when they use social networks.
    Many of the same rules that work for online chat work for these sites:
    ※Don't use your real name.
    ※ Don't give out personal information to people you don't know. A last name and a town are enough for a bad guy to find where you are.
    ※ Don't believe that people are who they say to be.
    ※ Immediately end any communication that makes you uncomfortable and report it to a parent.
   Only if you are sure of your safety, can you enjoy the fun brought by social networking. Besides, trying to deal with all problems on your own can lead to terrible results. Remember, asking your parents or school officials for help doesn't mean you are unable to do anything but wiser than many others.