Hershey and Chase Experiment
Until the mid-20th century, it was unsure among scientist whether DNA or proteins were responsible for carrying genetic material. In the year 1952, Alfred Chase, a bacteriologist and geneticist, and Martha Chase, a geneticist conducted an experiment that demonstrated that the genetic material for life was DNA instead of protein. In order to do this, they isolated two sets of T2 bacteriophage and radioactivelty labeled one set with radioactive sulfur, 35S, and the other with radioactive phosphours, 32P.
Moreover, bacteriophages are viruses that infects bacteria by injecting their contents inside of it in order to reproduce by programming the cells. They have a protein-covered coat and their DNA genome inside their core. Since sulfur is only found in the protein macromolecule and phosphorus is only found in the nucleic acids, the coat will be tagged with sulfur and the core will be tagged with phosphorus. The next part of the experiment involved them mixing the two sets of infected bacteria in a kitchen blender which agitated the phages in order to isolate the bacteria from them. Then, this mixture was put in a centrifuge to separate the contents by isolating the bacteria cells from the phage particles.
After analyzing this result, Hershey and Chase observed that the sulfur was predominant in the phages on the bottom of the centrifuge and that phosphorus was predominant in the infected bacteria cells, from where a new generation of infective bacteriophages are formed. They then concluded that DNA was the genetic material due to the phosphorus present in the cells, demonstrating a positive correlation between DNA and genetic material.
Until the mid-20th century, it was unsure among scientist whether DNA or proteins were responsible for carrying genetic material. In the year 1952, Alfred Chase, a bacteriologist and geneticist, and Martha Chase, a geneticist conducted an experiment that demonstrated that the genetic material for life was DNA instead of protein. In order to do this, they isolated two sets of T2 bacteriophage and radioactivelty labeled one set with radioactive sulfur, 35S, and the other with radioactive phosphours, 32P.
Moreover, bacteriophages are viruses that infects bacteria by injecting their contents inside of it in order to reproduce by programming the cells. They have a protein-covered coat and their DNA genome inside their core. Since sulfur is only found in the protein macromolecule and phosphorus is only found in the nucleic acids, the coat will be tagged with sulfur and the core will be tagged with phosphorus. The next part of the experiment involved them mixing the two sets of infected bacteria in a kitchen blender which agitated the phages in order to isolate the bacteria from them. Then, this mixture was put in a centrifuge to separate the contents by isolating the bacteria cells from the phage particles.
After analyzing this result, Hershey and Chase observed that the sulfur was predominant in the phages on the bottom of the centrifuge and that phosphorus was predominant in the infected bacteria cells, from where a new generation of infective bacteriophages are formed. They then concluded that DNA was the genetic material due to the phosphorus present in the cells, demonstrating a positive correlation between DNA and genetic material.
Displayed above are the three main steps of the Hershey and Chase experiment. The first step is where the bacteriophage infects the bacteria, the second step is where the phage heads are separated from the bacteria cells, and the third step is where the mixture is centrifuged to isolate to bacteria from the phage particles. Shown in red are the radioactively tagged element in each process, illustrating that sulfur was found in the phage protein coat, and phosphorus was found inside the bacteria cells.