Which scientist discovered bacterial transformation?

• A. Avery
• B. Bacteriophage
• C. Hershey-Chase
• D. Griffith

Answer: (D)

Transformation refers to the uptake of external DNA by a bacterium and the resulting heritable change in its traits. The major breakthrough showing that this phenomenon can occur in bacteria came from Frederick Griffith in 1928. In his experiment with Pneumococcus, he demonstrated that harmless bacteria could be converted into a virulent form when exposed to heat-killed virulent bacteria, implying the transfer of a heritable transforming substance. This established that genetic material could move between cells, even if the donor cells were no longer alive. Later work by Avery, MacLeod, and McCarty identified DNA as that transforming principle, and Hershey and Chase showed DNA is the genetic material in viruses, but the initial discovery of bacterial transformation is Griffith’s.