Creating hybrid genes by homologous recombination.

Recombination of homologous genes is a powerful mechanism for generating sequence diversity, and can be applied to protein analysis and directed evolution. In vitro recombination methods such as DNA shuffling are very flexible and can give hybrid genes with multiple crossovers; they have been used extensively to evolve proteins with improved and novel properties. In vivo recombination in both E. coli and yeast is greatly enhanced by double-strand breaks; for E. coli, mutant strains are often necessary to obtain high efficiency. Intra- and inter-molecular recombination in vivo have distinct features; both give hybrids with one or two crossovers, and have been used to study structure-function relationships of many proteins. Recently in vivo recombination has been used to generate diversity for directed evolution, creating a large phage display antibody library. Recombination methods will become increasingly useful in light of the explosion in genomic sequence data and potential for engineered proteins.