May 29, 1943: Luria-Delbrück Experiment Published Proving Random Mutations in Bacteria

On May 29, 1943, Italian-American geneticists Salvador Luria and Max Delbrück published the results of the Luria-Delbrück experiment (also known as the Fluctuation Test), demonstrating that the gene mutations in bacteria occur spontaneously and randomly. The experiment shown that, in bacteria, genetic mutations arise in the absence of selection, rather than being a response to selection. Which discovery significantly helped scientists further understand DNA replication and genetic evolution in bacteria, and proved that Darwin’s theory of natural selection acting on random mutations applies to bacteria as well as to other complex organisms. Together with Alfred Hershey, Salvador Luria and Max Delbrück won the 1969 Nobel Prize in Physiology or Medicine for this work.

Reference
https://en.wikipedia.org/wiki/Luria%E2%80%93Delbr%C3%BCck_experiment

Image Source
http://www.discoveryandinnovation.com/BIOL202/notes/lecture15.html