5-alpha Chemically Competent E. coli Cells for Cloning and Subcloning.AB 5 alpha chemically competent E. coli cells are comparable to the DH5_strain of E. coli. AB 5 alpha cells carry recA1 and endA1 mutations that minimize recombination and improve plasmid stability and quality. They also contain alacZ marker that provides _ complementation of the _ galactosidase gene for blue white color screening and are ideal for cloning, sub cloning, library construction, and plasmid isolation.