Original: The Hershey-Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase, confirming that DNA was the genetic material, which had first been demonstrated in the 1944 Avery-MacLeod-McCarty experiment.
Simplified: The Hershey-Chase experiments were a series of experiments started in 1952 by Alfred Hershey and Martha Chase. These experiments were to make sure that DNA was the genetic material which had first been discovered in the 1944 Avery-MacLeod-McCarty experiment.