Directed mutation

{{Evolution}}
'''Directed mutation''' (known in [[biology]] as '''directed mutagenesis''') is a hypothesis which proposes that organisms can respond to environmental stresses through directing [[mutation]]s to certain genes or areas of the genome. 

==History==

Directed mutation can be traced back to early [[non-Darwinian]] scientists such as [[Lev Berg]]<ref>Lev Semenovich Berg ''Nomogenesis: or, Evolution determined by law'' (1922)</ref> and [[Richard Goldschmidt]]<ref>Richard Goldschmidt ''The Material Basis of Evolution'' (1940)</ref> who claimed to have carried out experiments proving directed mutation with drosophila or other species; however their results were unable to be replicated by other scientists and the hypothesis of directed mutation fell from favour.

It was revived in the 1980's when the geneticist John Cairns wrote a paper due to his experiments on Escherichia coli [[bacteria]] advocating the view that bacteria in response to environmental stresses can actively induce genetic mutations in selected genes in an effort to survive. He later changed his views about the mutations and described them as evidence for "Adaptive Mutation". Later research in 2006 showed that Cairns' observation of apparently adaptive mutations could be explained by "a conventional Darwinian process" known as amplification mutation.<ref>[http://www.pnas.org/content/99/4/2164.full Amplification–mutagenesis: Evidence that “directed” adaptive mutation and general hypermutability result from growth with a selected gene amplification]</ref> However another paper published in 2007 rejected the amplification mutation explanation and wrote ""mutants that appear during the first few days of lactose selection are true revertants that arise in a single step".<ref>[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1899370/ Amplification of lac Cannot Account for Adaptive Mutation to Lac+ in Escherichia coli]</ref>

==Current status==

The hypothesis of directed mutation is currently under investigation. Although environmental stresses appear to be able to increase the rate of mutation in a "directed" manner at various actively transcribed gene, to this day, there are no evidence that implies this is due to any conscientious decision. 

The theory of "directed mutation" by Cairns and his collaborators (1998) has now fallen out of favour in our evolutionary thinking and the original results from their study have been explained in a Neo-Darwinian terms. Nonetheless, their experiments motivated scientists to question the independence of mutation to the selective pressure in the environment.  As a result, several evidences have now been accumulated that sheds light on the fact that the mutation rate varies along a genome (i.e. there are hotspots where mutation is more likely), and that this variation can be subject to selection by the environment. It has been suggested that organisms might evolve lower mutation rates at loci where mutations are most deleterious or increased rates where mutations are most needed.
<ref>http://onlinelibrary.wiley.com/doi/10.1002/bies.201200150/abstract</ref>
The term directed mutation, have been mostly replaced to "adaptive" mutation in the scientific community.<ref>http://www.nature.com/nrg/journal/v14/n3/full/nrg3415.html</ref>

===Intelligent design===

Directed mutation has been considered by some [[intelligent design]] advocates such as [[Michael Behe]] in his book ''[[The Edge of Evolution]]'' (2007). Young earth [[creationist]]s such as [[Ken Ham]] believe mutations originated by a curse (Genesis 3) in the Bible and deny that they cause evolution.<ref>[http://www.answersingenesis.org/articles/nab2/mutations-engine-of-evolution One such example] of this nonsense</ref>

===New age===

Directed mutation has also been supported by some fringe scientists and [[new age]] authors who proclaim that organisms themselves can direct mutations via organizing principles, immaterial fields or by [[consciousness]].<ref>[http://integral-review.org/documents/padelford,%20consciousness%20in%20evolution,%20vol.%205,%20no.%202.pdf Consciousness in Evolution Sketch for a New Model – A Speculation by Donald F. Padelford]</ref> The physicist Amit Goswami published a paper titled ''Is there conscious choice in directed mutation, phenocopies, and related phenomena? An answer based on quantum measurement theory'' (1997).<ref>[http://www.ncbi.nlm.nih.gov/pubmed/9229240 Is there conscious choice in directed mutation, phenocopies, and related phenomena? An answer based on quantum measurement theory by Amit Goswami and Dennis Todd]</ref> These views have been considered fringe or [[pseudoscience]] by most other scientists.{{fact}}

==See also==
*[[Hopeful monster]]

==External links==
*[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC205770/ Directed Mutation: Between Unicorns and Goats]
*[http://nsm.uh.edu/~dgraur/pdf/sniegowski_lenski_1995.pdf Mutation and Adaptation: The Directed Mutation Controversy in Evolutionary Perspective]

==References==
{{reflist|2}}
[[Category:Biology]]

Categories: Biology