Practice question

Frederick Griffith in 1928 mixed heat-killed virulent smooth S Streptococcus pneumoniae bearing polysaccharide capsule with live avirulent rough R noncapsulated strain and injected into mice. R alone was harmless, but mixture killed mice and yielded live S recovered from blood. Heat-stable substance from dead S transformed R genotype to S, acquiring capsule genes and virulence heritably. This phenomenon was named transformation, first demonstration bacteria exchange genetic traits. Later Avery identified material as DNA, but Griffith established principle of horizontal genetic information transfer.