The Luria-Delbrück experiment

The Luria-Delbrück experiment demonstrated that genetic mutations in bacteria occur spontaneously, not caused by exposure to antibiotics. They grew bacteria and then exposed different cultures to the antibiotic. If mutations happened because of the antibiotic, all cultures would have similar resistant bacteria. Instead, they found some cultures had many resistant bacteria while others had none, indicating mutations occurred randomly before exposure. This experiment supported the idea that genetic changes happen naturally, not as a direct response to environmental pressure, foundational for understanding mutation and evolution in biology.