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问:在噬菌体侵染细菌的实验中,怎样知道进入细菌细胞的是噬菌体的DNA而不是蛋白质呢?答:噬菌体是有蛋白质的外壳包裹着DNA的简单结构.它侵染细菌时,进入细胞的是DNA还是蛋白质呢?美国科学家赫尔希(Hersher)和蔡斯(Chase)在1952年做了如下的实验回答了这个问题.他首先将噬菌体培养在含有用~(32)P同位素标记的磷酸盐培养基上,结果DNA被~(32)P标记.而蛋白质一般只是由C、H、O、N、S元素组成,而不含P,故蛋白质不会被标记.他又将噬菌体放在含有~(35)S同位素标记的硫酸盐培养基里培养,结果噬菌体的蛋白质被~(35)S标记上.而DNA没有被标记.
Q: How do you know the bacteriophage DNA, not the protein, that enters the bacterial cell in the experiment of bacteriophage infecting bacteria? A: Bacteriophage is a simple structure in which a protein shell encapsulates DNA. When it infects a bacterium, it enters the cell DNA or protein? American scientists Hersher and Chase responded to this question by doing the following experiment in 1952. He first cultivated bacteriophages in a solution containing phosphate labeled with ~ (32) P Salt medium, the resulting DNA is labeled with ~ (32) P. The protein is generally composed of elements C, H, O, N, S without P, so the protein is not labeled and in turn puts the phage on Sulfate medium containing ~ (35) S isotope labeling showed that phage protein was labeled with ~ (35) S, while DNA was not labeled.