Cue Column | Note Column

Who proved what? | Griffith (1928): Discovered the "transforming principle" (did NOT identify the molecule). Avery, MacLeod, McCarty (1944): Proved the transforming principle is DNA (only DNase destroyed activity). Hershey & Chase (1952): Confirmed DNA = genetic material using ^32P (DNA) and ^35S (protein) with T2 phage.

What was the key control in Avery's experiment? | Three parallel treatments: DNase → transforming ability LOST; Protease → ability retained; RNase → ability retained. Conclusion: DNA is the active molecule.

What was the key result in Hershey-Chase? | After phage infection + blending + centrifugation: ^32P in pellet (bacteria); ^35S in supernatant (phage coats). DNA entered bacteria; protein stayed outside.

Summary:

The three landmark experiments form a logical sequence: Griffith discovered transformation → Avery identified the chemical → Hershey-Chase delivered the definitive physical proof. Always trace this historical arc in NEET answers.