Simplified generation of targeting constructs using ET recombination.

ET recombination is a way to engineer DNA in Escherichia coli using homologous recombination. Here we develop the potential of ET recombination in two ways relevant to complex engineering exercises such as building gene targeting constructs. First, a targeting construct was made in a single step. Second, ET recombination was used to place two unique restriction sites at precise positions in a large genomic clone. Subsequently a complex targeting construct was created by ligation with a multifunctional cassette.