Input (grade 13): The Luriaâ "DelbrÃ 1\/4 ck experiment (1943) (also called the Fluctuation Test) demonstrates that in bacteria, genetic mutations arise in the absence of selection, rather than being a response to selection.
Output (grade 10): The Luriaâ "DelbrÃ 1\/4 ck experiment, 1943, asks the question: are mutations independent of natural selection? Or are they directed by the selection?