Question

What technique did Hershey and Chase use in their experiment that led to the conclusion that DNA, not protein, was the genetic material in viruses?

Answer 1

Chase and Hershey labeled DNA with radioactive phosphorus and proteins with radioactive sulfur. They found that after virus infection of bacteria, only the labeled DNA entered the bacterial cells, providing strong evidence that DNA, not protein, was the genetic material.

Step-by-step explanation:

Hershey and Chase Experiment

In 1952, Martha Chase and Alfred Hershey conducted experiments that led to the conclusion that DNA, not protein, was the genetic material in viruses. They studied the T2 bacteriophage, a virus that infects E. coli cells, which consists of a nucleic acid core and a protein coat. Hershey and Chase cleverly devised a technique where they labeled the DNA of one batch of phages with radioactive phosphorus (32P), and the proteins of another batch with radioactive sulfur (35S). During the experiment, batches of T2 bacteriophages infected E. coli cells, and after some time, a blender was used to detach the phage coats from cells. The mixture was then centrifuged to separate the heavier bacterial cells from lighter phage particles. In the batch with labeled proteins, radioactivity was found only in the supernatant, showing that proteins did not enter the cell. Conversely, in the batch with labeled DNA, radioactivity was found inside the bacterial cells, indicating that DNA was the component that entered the cells. This study provided compelling evidence that DNA is the material carrying genetic information and led to a broader acceptance of DNA as the hereditary molecule.

Answer 2

They used radioactive labeling techniques to build two different types of phage.

Step-by-step explanation:

In 1952, a set of experiments were carried out by American biochemists Alfred D. Hershey (1908-1997) and Martha Chase. They prepared two separate virus samples, one contained DNA labeled with a radioactive isotope and the other contained protein labeled with a different radioactive isotope. They grew the two types of viruses separately, infected bacteria with the two sets of phages and analyzed the bacteria for radioactivity. From the results obtained, Hershey and Chase concluded that the viral genetic material was DNA and not protein, reinforcing the observations previously made by Avery.