分子生物学(中英对照有备注)2.pptVIP

* Another experiment, called the Hershey-Chase experiment showed that DNA alone can hold the information to make a whole virus. It was known that viruses called phages can replicate inside a bacterial cell. The phages inject some material into the bacteria, and that material is used to make new viruses. 另一个实验即Hershey-Chase实验显示，单单DNA就能保存用于产生整个病毒的信息。已经知晓，被称为噬菌体的病毒在细菌的帮助下进行复制。噬菌体注射某种物质到细菌的体内，这种物质被用于产生新的病毒。 * The Hershey-Chase experiment showed that when phages replicate, they only need to inject their DNA into the host cells; no protein is transmitted. Hershey-Chase实验显示，当噬菌体复制的时候，它们只需要将它们的DNA注射到宿主细胞中；并没有进行蛋白质的传递。 * This was shown by making two preparations of virus. One was grown using radioactive phosphorous. Because only DNA contains phosphorous, the radioactive medium specifically labeled DNA in the phages. In another preparation, viruses were grown using radioactive sulfur. Only proteins contain sulfur, so this specifically labeled protein in these viruses. 这是通过使用两种病毒样本得到证明的。一种样本生长在用放射性磷做标记的培养基中。由于只有DNA含有磷，蛋白质不含磷，因此这种放射性培养基特异性地对噬菌体中的DNA进行标记。另一种样本的病毒生长在用放射性硫做标记的培养基中。只有蛋白质含有硫，DNA不含硫，所以这种培养基特异性地标记蛋白质。 * Next, each preparation was used to infect bacteria. After some time, the mixtures were spun at high speeds to separate the bacteria from the viruses. In the mixture that contained viruses with radioactive phosphorous, radiation was detected mostly inside the bacteria. This meant that DNA was injected into the bacteria. In the experiment that used viruses with radioactive sulfur, radiation was found only outside the bacteria, in the original phages. This means that viral proteins did not enter the bacteria. 下一步，每种病毒样本都用来侵染细菌。侵染了一段时间后，将得到的混合物高速离心而把细菌和病毒分开。在用含有放射性磷做标记的病毒进行侵染得到的混合物中，放射性主要存在于细菌体内，意味着DNA被注射到了细菌体内。在用含有放射性硫的病毒所做的侵染实验中，放射性只存在于细菌外面，位于原先那些病毒体内。这意味着病毒的蛋白质并没有进入细菌内部。 * Because whatever material injected by viruses into bacteria is used to make new viruses, this shows that the DNA carries all the information for how to make a new virus. 由于不管是什么物质被病毒