The Luria-Delbrück experiment: are mutations spontaneous or directed? (Q999211)

Summary: Where do mutations come from and what do they have to do with mathematics? The answer is `a lot', as this article will demonstrate. Indeed, it was a historical milestone of mathematical biology that revealed some fundamental insights into the nature of mutations during the 1940s. An unresolved question in those days was: `Are mutations due to directed adaptation to environmental change or do they occur spontaneously, in a random way?' Today, the answer is basic knowledge in genetics and many textbooks briefly describe the crucial experiment, along with some plausibility arguments. It is less well-known, however, that it was a fascinating interaction of theory and experiment that made this breakthrough possible. This is what will be described here.