the transforming principle was first witnessed in 1928 by Frederick Griffith during a series of experiments with Streptococcus pneumoniae (also known as Diplococcus pneumoniae or pneumococcus) . Griffith observed that heat-killed S strain bacteria could transform live R strain bacteria into a virulent form, enabling the R strain to synthesise a smooth polysaccharide coat . This discovery was later refined by Avery, MacLeod, and McCarty, who proved that DNA was the transforming substance . This is a fundamental concept in molecular biology, and mastering it is a high-priority strategy as NCERT textbooks serve as the primary source for approximately 95% of NEET Biology questions .