Joined: May 2002
Charlie D gives a great brief intro on why adaptive mutation ain't:
Topic: Directed mutation
Originally posted by charlie d:
I have no idea when that paper was written, but it lists no references later than 1995. Thus, its enthusiasm for the "targeted mutation" phenomenon, its belief that it represents a fundamental challenge to the prevailing genetic paradigm, and its conclusion that "there is no explanation for it", is not surprising, considering that the hypothesis itself began to crumble in earnest in 1996 with the publication of this article by Prival and Cebula:
Prival MJ, Cebula TA Adaptive mutation and slow-growing revertants of an Escherichia coli lacZ amber mutant. Genetics 1996 Dec;144(4):1337-41,
and eroded further after this article by Patricia Foster (who was one of the original discoverers of the adaptive mutations phenomenon):
Foster PL. Nonadaptive mutations occur on the F' episome during adaptive mutation conditions in Escherichia coli. J Bacteriol. 1997 Mar;179(5):1550-4.
These and other findings prompted Foster herself to write the now classic review (available for free here): Foster PL. Adaptive mutation: has the unicorn landed? Genetics. 1998 Apr;148(4):1453-9,
a virtual obituary for the "lamarckian" interpretation of the phenomenon.
A more detailed review is this one (but subscription is required to access the actual paper): Foster PL. Mechanisms of stationary phase mutation: a decade of adaptive mutation. Annu Rev Genet. 1999;33:57-88.
At the current state of affairs, it is very clear that mutations during "adaptive mutagenesis" are not specifically directed towards the gene(s) under selection, i.e. they are entirely darwinian (random wrt to fitness), and are often the result of generalized hypermutation mechanisms (the last important piece of the puzzle being the publication of this paper last year): Hendrickson H, Slechta ES, Bergthorsson U, Andersson DI, Roth JR. Amplification-mutagenesis: evidence that "directed" adaptive mutation and general hypermutability result from growth with a selected gene amplification. Proc Natl Acad Sci U S A. 2002 Feb 19;99(4):2164-9.
For those interested in the most recent and actual history of the "targeted mutation" saga, I recommend this recent excellent review of the issue, available for free here: Rosenberg SM Evolving responsively: adaptive mutation. Nat Rev Genet 2001 Jul;2(7):504-15
Edited by niiicholas on Jan. 25 2003,18:01