In 1952 Alfred Hershey and Martha Chase devised an experiment to study the reproduction of the bacteriophage. The experiment used isotopes of phosphorus (32P) and sulphur (35S) to follow the protein component of the bacteriophage (which contains sulfur and no phosphorus) and the DNA component (which contains phosphorus and no sulphur) during an infection. The bacteriophage was obtained by growing T2 from E. coli in the presence of the isotopes.
In phage infection the bacteriophage attaches to the bacterial cell and inserts its DNA into the cell, leaving the protein coat attached to the outside of the cell. Hershey and Chase mixed their labeled T2 with E. coli and then centrifuged the mixture to separate the bacteriophage protein from the E. coli, which now contained the bacteriophage DNA. The experiment found that 20% of the labeled phosphorus and only 1% of the labeled suphur was in the bacteria, showing that the protein coat plays no direct role in bacteriophage reproduction, and that DNA was the sole material of heredity.
- Garrett, R.H. & C.M. Grisham, 1998. Biochemistry, 2nd ed. Saunders College Publishing, Orlando FL. Ch 29.
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