本题目来源于试卷: Unity and Diversity A.2 Nucleic Acids，类别为 IB生物学
[单选题]
Hershey and Chase conducted experiments usinjrc+ ourpg* 3 vp 9,f-*icto9vg the rad6agybm2 lh43fc2u8m jioactive isotopes $^{35}$S and $^{32}$P which demonstrated that DNA is the genetic material. What would they have observed about the distribution of isotopes in the centrifuged sample if protein, rather than DNA, were the genetic material?
A. High proportion of $^{35}$S in the bacterial pellet relative to the supernatant.
B. High proportion of $^{32}$P in the bacterial pellet relative to the supernatant.
C. High proportion of both $^{35}$S and $^{32}$P in the bacterial pellet relative to the supernatant.
D. Low proportion of both $^{35}$S and $^{32}$P in the bacterial pellet relative to the supernatant.
参考答案: A
本题详细解析:
Hershey and Chase grew bacteriophages in the presence of the radioactive isotojeubv.t 8/z .tpeb./ .zut8je vt $^{35}$S or $^{32}$P, then allowed them to infect bacteria. If proteins, rather than DNA, had been the genetic material transferred to bacteria, the bacteria would have contained $^{35}$S (the radiolabel in proteins) and not32P (the radiolabel in DNA). Therefore, Hershey and Chase would have observed a high proportion of $^{35}$S in the bacterial pellet relative to the supernatant.A high proportion of $^{32}$P in the bacterial pellet relative to the supernatant (Choice B) indicates that DNA, not protein, was the genetic material. Hershey and Chase did not grow bacteria in the presence of both isotopes at the same time and so could not have observed either a higher (Choice C) or lower (Choice D) proportion of both $^{35}$S and $^{32}$P in the bacterial pellet relative to the supernatant.
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