What is Directed evolution?
[[File:DE cycle.png|thumb|400px|An example of directed evolution with comparison to [[evolution|natural evolution]]. The inner cycle shows the three stages of the directed evolution cycle with the mimicked natural process in brackets. The outer circle shows steps in a typical experiment. The red symbols indicate functional variants, the pale symbols indicate variants with reduced function]] '''Directed evolution''' ('''DE''') is a method used to produce [[enzymes]] for industrial or medical purposes. The method is [[protein]] [[engineering]] which [[mimic]]s [[natural selection]].<ref>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2982887/ Stephen Lutz 2010. Beyond directed evolution - semi-rational protein engineering and design. ''Curr Opin Biotechnol''. '''21'''(6): 734–743.]</ref> The basic idea is to put a [[gene]] through repeated rounds of [[mutation]], to make a library of variants. Selection isolates genes with the desired function. They are a [[template]] for the next round.<ref>{{cite journal |last=Voigt C.A; Kauffman S. & Wang Z.G. 2000 |title=Rational evolutionary design: the theory of in vitro protein evolution|journal=Advances in Protein Chemistry |year=2001|volume=55|pages=79–160|pmid=11050933|doi=10.1016/s0065-3233(01)55003-2|isbn=9780120342556}}</ref> This can be done ''in vivo'' (in living cells of [[bacteria]] or [[yeast]]), or ''in vitro'' (free in solution or microdroplets). Testing more mutants increases the chances of finding one with the desired properties.<ref>{{cite journal|last= Dalby P.A. 2011 |title=Strategy and success for the directed evolution of enzymes|journal=Current Opinion in Structural Biology |year=2011|volume=21|issue=4|pages=473–80| pmid=21684150|doi=10.1016/j.sbi.2011.05.003}}</ref> During ''in vivo'' evolution, each cell (usually [[bacteria]] or [[yeast]]) is [[Transformation (genetics)|transformed]] with a [[plasmid]] containing a different member of the variant library. Only the gene of interest differs between the cells, with all other genes being kept the s