Hershey and Chase Experiment
Even after the compelling evidence provided by the Avery, Macleod and McCarty
experiment, there were still a few skeptics out there who weren’t convinced. The
debate still raged between proteins and DNA. However, the Hershey and Chase
experiment permanently put an end to this long-standing debate.
Alfred Hershey and Martha Chase in 1952, performed an experimentthat proved,
without a doubt, that DNA was the carrier of information. For their experiment,
they used the bacteriophage T2. A bacteriophage is a virus that only infects
bacteria. This particular virus infectsEscherichia coli. T2 had a simple
structurethat consisted of just 2 components – an outer protein casing and the
inner DNA. Hershey and Chase took 2 different samples of T2. They grew one
sample with32P, which is the radioactive isotope of phosphorus, and the other
sample was grown with35S, the radioactive isotope of sulfur for many
generations.
The protein coat has sulfur and no phosphorus, while the DNA material has
phosphorus but no sulfur. Thus, the 2 samples were labelled with 2 different
radioactive isotopes.
The viruses were then allowed to infect theE. coli. Once the infection was done,
the experimental solution was subjected to blending which removed the protein
