[问答题]
The Hershey-Chase exper
m0j9evx c unmym:(l)4nj a62aiment in 1952 involv
n- e2 u j4(l0it;gbyot+dyq2xed cultured viruses that were radioactively labelled with either sulfur (
-juy4; (+2q2 ngoeytl bid0 tx$^{35}$S) or phosphorus ($^{32}P) in two separate flasks. Each batch of viruses was then added to separate cultures of bacteria. After allowing time for the viruses to infect the bacteria, the culture solutions were centrifuged to separate the viral remains from the bacterial cells, forming two layers, the pellet and the supernatant.
1.State reasons for using radioactive sulfur ($^{35}$S) and phosphorus ($^{32}$P).
2.Suggest one technological development, other than radioisotopes, that helped open up possibilities in understanding the overall structure of DNA.
3.1.Outline the results of the experiment that provided evidence to support the conclusion that DNA is the genetic material.
3.2.Describe how the 4 nitrogenous bases of DNA enables polypeptides to be coded for.
4.Explain how DNA can be packaged into compact units to form chromatin.