The random origin of mutations versus directed mutations

Luria & Delbrück in 1941.
Original repository:
Cold Spring Harbor Laboratory Archives

Do mutations arise randomly with respect to their fitness effects (undirected mutations), or do organisms acquire mutations that are favorable upon exposure to a new environment (directed mutations)? Most of our current knowledge of evolution and genetics relies on undirected origin of mutations. The Central Dogma, as we know it now, wouldn’t exist if mutations were directed. The question remained largely unanswered until 1943, until Salvador Luria and Max Delbrück conducted an experiment, which, along with their subsequent work, won them the Nobel prize in 1969. This was before DNA was identified as the carrier of genetic information, and we still didn’t know whether prokaryotes and eukaryotes used the same genetic material. The experiment was a brilliant integration of simple microbiology, probability theory and a phylogenetic context. Surprisingly, the experiment used little more technology beyond plating out E. coli with a bacteriophage and counting how often resistant bacterial mutants arose.

• The original paper   - http://www.genetics.org/content/28/6/491.full.pdf+html

 A "recent" review by Lenski & Mittler about the reignited directed mutation controversy. Gives a good summary of the Luria-Delbrück experiment too. - http://lenski.mmg.msu.edu/lenski/pdf/1993,%20Science,%20Lenski%20&%20Mittler.pdf