Question

Hershey and Chase used radioactive ³⁵S and ³²P in experiments to provide evidence that DNA was the genetic material. These experiments pointed to DNA because:
A. Progeny viruses retained ³²P but not ³⁵S
B. Retention of ³²P in progeny viruses indicated that DNA was passed on.
C. Loss of ³⁵S in progeny viruses indicated that proteins were not passed.
D) All of the above

Answer 1

Hint: DNA is made of nucleotides. Nucleotides contain nitrogen bases, a pentose sugar and phosphate group. Some amino acids such as cysteine, cystine and methionine have sulphur in them. Radiolabelled phosphorous and sulphur helps to know if DNA or protein is the genetic material.

Complete Step by Step Answer:
Hershey and Martha Chase used radiolabelled phosphorous and sulfur to conclude that DNA is the genetic material. They used two different E. coli cultures. One with radiolabelled phosphorous and the other with sulphur. Radiolabelled phosphorous will get incorporated into the DNA and radiolabelled sulfur will get incorporated into the protein. Now, these cells were infected with bacteriophages. They multiply in the host cell. One set will have radiolabelled phosphorous and the other one will have radiolabelled sulfur.

These were then introduced in separate cultures having unlabelled bacteria. After the infection, the cells were centrifuged. So the heavier bacteria clumped at the bottom and the supernatant had the viral coats in it which did not enter the cell. It was observed that the cells had radiolabelled phosphorous and the supernatant had radiolabelled sulfur in them.
From this experiment, it was concluded that the progeny virus retained the radiolabelled phosphorous and not the sulfur. As stated earlier, radiolabelled phosphorous was incorporated into the DNA. And radiolabelled sulfur was absent indicating proteins are not the genetic material but DNA is.

Hence, The correct option is D.

Note: Bacteriophage is a virus that infects bacteria. It uses all the bacteria’s machinery to duplicate itself. Bacteriophage has a coat and genetic material inside it. While infecting, it leaves its coat outside and only genetic material can enter the cell.