Replica plate experiment by Lederberg showing antibiotic resistance proves

Replica plate experiment was conducted by Joshua Lederberg and Esther Lederberg in 1952. This demonstrated the genetic basis of drug-resistant mutation in Esherichia coli bacteria. This experiment proved that he antibiotic-resistant strains of bacteria were able to survive antibiotics because these bacteria has the resistance before their exposure to it. This is an example of natural selection.