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.[4]


  1. ^ Wertz J. "Strain - DH5α". The Coli Genetic Stock Center (CGSC). Yale University. Retrieved 2017-05-23.
  2. ^ Chan WT, Verma CS, Lane DP, Gan SK (December 2013). "A comparison and optimization of methods and factors affecting the transformation of Escherichia coli". Bioscience Reports. 33 (6). doi:10.1042/BSR20130098. PMC 3860579. PMID 24229075.
  3. ^ Bryant FR (June 1988). "Construction of a recombinase-deficient mutant recA protein that retains single-stranded DNA-dependent ATPase activity" (PDF). The Journal of Biological Chemistry. 263 (18): 8716–8723. doi:10.1016/S0021-9258(18)68364-4. PMID 2967815.
  4. ^ Taylor RG, Walker DC, McInnes RR (April 1993). "E. coli host strains significantly affect the quality of small scale plasmid DNA preparations used for sequencing". Nucleic Acids Research. 21 (7): 1677–1678. doi:10.1093/nar/21.7.1677. PMC 309390. PMID 8479929.