Creating a Library of Diverse Solutions

Before the introduction of the polymerase chain reaction (PCR)[351, point mutations were usually produced by UV radiation, by chemical treatment1451 or by using mutator strains that have an increased mutation rate compared to normal strains because of defects in their DNA-repair mechanisms1461. Chemical mutagenesis1471, mutator strains148, 491, and even spontaneous mutations coupled with selection in a 

Random point mutagenesis None Exhaustive No multiple simultaneous mutations requires multiple rounds to accumulate beneficial mutations 

Focused mutagene- Structural informa- Reduced library Misses possible 

The optimal mutation rate depends on fitness of the parental sequence. For a sub- 

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