TRANSFORMATION EXPERIMENTS
- After Griffith’s experiments, Oswald Avery and his colleagues became interested in discovering which constituent in the heat-killed virulent pneumococci was responsible for transformation.
- To investigate this question, they used enzymes to selectively destroy DNA, RNA, or protein in purified virulent pneumococci (S strain) extracts.
- They then exposed non-virulent pneumococcal strains (R strains) to the treated extracts to determine whether transformation occurred.
- Interestingly, the transformation of the non-virulent bacteria was blocked only if DNA was destroyed, suggesting that DNA was carrying the information required for transformation.
- This observation provided strong evidence that DNA was the genetic material responsible for transmitting hereditary information.
- In 1944, Avery, C. M. MacLeod, and M. J. McCarty published their findings in a paper titled “Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Deoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III.”
- This paper was a landmark in the history of molecular biology, as it was the first to show that DNA carried genetic information.
- The discovery by Avery and his colleagues paved the way for further research into the structure and function of DNA and led to the development of the field of molecular genetics.
- Avery’s work also had practical implications, as it provided a basis for understanding the mechanisms of antibiotic resistance in bacteria and the development of vaccines against bacterial infections.
- Overall, Avery and his colleagues’ work built on Griffith’s findings and provided the first conclusive evidence that DNA was the genetic material responsible for transmitting hereditary information.
