In Hershey and Chase's experiment investigating which biological molecule carries genetic information, they found that phage DNA with radiolabeled phosphorus was retained in bacterial cells after transduction. To conclude that DNA is the genetic material, what assumption did they have to make?

A. Protein does not enter the bacterium during transduction.

B. DNA does not stay in the media after transduction.

C. All of the phage DNA was radiolabeled.

D. Bacteria can be transduced by phage.

The correct answer would be A. Protein does not enter the bacterium during transduction.

In their experiment, Hershey and Chase labeled protein coat as well as DNA of the bacteriophage with radioactive sulfur and phosphorus respectively.

They concluded that DNA was the genetic material as only radioactive phosphorous was found in the bacteria after transduction.

In addition, radioactive sulfur or protein was not found in the bacterial cells and thus, they could conclude that protein was not genetic material.

Thus, presence of viral DNA and absence of viral proteins were both required in order to conclude that DNA was the genetic material.