DH5-Alpha Cell

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DH5-Alpha Cells are E. coli cells engineered by American biologist Douglas Hanahan to maximize transformation efficiency. They are defined by three[1] mutations: recA1, endA1 which help plasmid insertion and lacZΔM15 which enables blue white screening. The cells are competent and often used with calcium chloride transformation to insert the desired plasmid. A study of four transformation methods and six bacteria strains showed that the most efficient one was the DH5 strain with the Hanahan method.[2]


  • The recA1 mutation is a single point mutation that replaces glycine 160 of the recA polypeptide with an aspartic acid residue[3] in order to disable the activity of the recombinases and inactivate homologous recombination.
  • The endA1 mutation inactivates an intracellular endonuclease to prevent it from degrading the inserted plasmid.


  1. ^ "Strain - DH5α". cgsc2.biology.yale.edu. Retrieved 2017-05-23.
  2. ^ Chan, Weng-Tat; Verma, Chandra S.; Lane, David P.; Gan, Samuel Ken-En (2013-12-12). "A comparison and optimization of methods and factors affecting the transformation of Escherichia coli". Bioscience Reports. 33 (6). doi:10.1042/BSR20130098. ISSN 0144-8463. PMC 3860579. PMID 24229075.
  3. ^ Bryant, Floyd (November 9, 1987). "Construction of a Recombinase-deficient Mutant recA Protein That Retains Single-stranded DNA-dependent ATPase Activity" (PDF). Journal of Biological Chemistry.