Question

What is the evidence that indicates DNA is the primary genetic material?

Answer 1

The evidence that DNA is the primary genetic material comes from several landmark experiments that shifted the scientific consensus away from proteins:

• Griffith’s Transformation Experiment (1928): Demonstrated that a “transforming principle” could transfer heritable traits (virulence) from dead bacteria to live ones, though he didn’t identify the molecule.
• Avery, MacLeod, and McCarty Experiment (1944): Building on Griffith’s work, they used digestive enzymes to show that only the destruction of DNA (not proteins or RNA) prevented transformation. This was the first direct biochemical evidence.
• Hershey-Chase Experiment (1952): Used radioactive isotopes (32P for DNA and 35S for protein) to track bacteriophage infection. They proved that only the viral DNA entered the bacteria to produce new viruses, while the protein shell stayed outside.
• Chargaff’s Rules: Showed that DNA composition is species-specific and follows fixed base-pairing ratios (A = T and C = G), suggesting a stable and universal method for storing information.