How did they find that DNA was genetic material? Transformation?

- by studying bacteria and the viruses that​ infect them - Frederick Griffith (worked with two strains of a bacterium, one pathogenic [cause disease] and one harmless) - mixed killed remains of pathogenic strain with living cells of harmless strain - some living cells ended up becoming pathogenic - He called this phenomenon transformation (now defined as a change in genotype and phenotype due to assimilation of foreign DNA​) - work by later scientists identified the transforming substance as DNA (some biologists were skeptical though bc there wasn't a lot of info on DNA)