Describe the various steps of Griffith's experiment that led to the conclusion of the 'Transforming Principle'. How did the chemical nature of the 'Transforming Principle' get established?

(a) Griffith proved the presence of a transforming principle in bacteria that leads to genetic transformation. He infected mice with a mixture of virulent (SIII) and non-virulent strains (RII) of Streptococcus pneumoniae. Heat-killed SIII did not cause any infection, but a mixture of heat-killed SIII and living RII strains caused infection because a transforming substance was transferred from the heat-killed strain to the non-virulent strain, causing the non-virulent strain to transform into a virulent form. There was no direct physical contact between virulent and non-virulent strains during the transfer of genetic material. (b) The follow-up experiment by Avery, McLeod, and McCarty and Hershey and Chase established that DNA is the transforming principle, not proteins as it was assumed to be.