Luria-Delbrück experiment

The Luria-Delbrück experiment tested whether genetic mutations occur spontaneously or in response to environmental stress. They grew bacteria in separate cultures and then exposed each to a virus. If mutations happened as a response, each culture should have a similar number of resistant bacteria. Instead, they found some cultures had many resistant bacteria while others had few, supporting that mutations occur randomly before encountering the virus. This experiment demonstrated that genetic changes in bacteria happen naturally and unpredictably, not as a direct reaction to environmental pressure, fundamentally influencing our understanding of evolution and genetics.