Hershey-Chase performed an experiment on------------------.

The unequivocal proof that DNA is the genetic material came from the experiments of Alfred Hershey and Martha Chase in 1952.

They worked with viruses that infect bacteria, which are called bacteriophages (specifically the T2 bacteriophage).

In their experiment, they used radioactive isotopes of phosphorus (^{32}$\text{P} ) and sulfur (^{35}\text{S}$) to label the DNA and protein coat of the bacteriophages, respectively, to determine which of these molecules enters the bacterial cell (Escherichia coli) during infection.

Answer: Bacteriophages