Question

Problem 1. What would have been the result of Hershey & Chase experiment if protein, not DNA were the genetic material?

A) 32P → labeled phage protein → radioactivity in cells 35S → labeled phage DNA → radioactivity in phage ghosts

B) 32P → labeled phage protein → radioactivity in phage ghosts 35S → labeled phage DNA → radioactivity in cells

C) 32P → labeled phage DNA → radioactivity in cells 35S → labeled phage protein → radioactivity in phage ghosts

D) 32P → labeled phage DNA → radioactivity in phage ghosts 35S → labeled phage protein → radioactivity in cells

Problem 2. Your goal is to obtain ³²P-radioactively labeled DNA. To do this, you carry out in vitro DNA replication in the presence of ³²P-radioactively labeled nucleotides, in which one of the phosphates is labeled with ³²P-radioactive phosphorus. Which phosphate group should be radioactive?

A) Alpha-phosphate

B) Beta-phosphate

C) Gamma-phosphate

D) All three options above will produce radioactively labeled DNA

Problem 3. Suppose that cells are grown in culture in the presence of radioactive nucleotides for many generations so that both strands of every DNA molecule include radioactive nucleotides. The cells are then harvested and placed in new medium with nucleotides that are not radioactive so that newly synthesized DNA will not be radioactive. What fraction of DNA molecules will contain radioactivity after two rounds of replication?

Answer 1

1)D)32P-> labelled phage DNA>radioactivity in phage ghost

35S->lebelled phage protein->radioactivity in cells.

In thus experiment protein is labeled with 35S and DNA with 32P.if protein is genetic material then it must enter the bacteria and bacteria will become radioactive (35S).and the DNA will not enter and its radioactivity will be retained in phage ghost (32P).

2)A)alpha phosphate

During DNA replication tge phosphate that forms phosphodiester bond is alpha phosphate. Beta and gamma phosphate are removed when 3'OH is added to form bond.

3)2/4

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