<Li> Altering substrate specificity of existing enzymes, (often for use in industry) </Li> <P> The study of natural evolution is traditionally based on extant organisms and their genes . However, research is fundamentally limited by the lack of fossils (and particularly the lack of ancient DNA sequences) and incomplete knowledge of ancient environmental conditions . Directed evolution investigates evolution in a controlled system of genes for individual enzymes, ribozymes and replicators (similar to experimental evolution of eukaryotes, prokaryotes and viruses). </P> <P> DE allows control of selection pressure, mutation rate and environment (both the abiotic environment such as temperature, and the biotic environment, such as other genes in the organism). Additionally, there is a complete record of all evolutionary intermediate genes . This allows for detailed measurements of evolutionary processes, for example epistasis, evolvability, adaptive constraint fitness landscapes, and neutral networks . </P>

Continuous directed evolution for strain and protein engineering