I can not find some useful sources unfortunately.

Please tell me about some important characteristics of DH5 alpha.

What makes DH5 alpha suitable for the gene cloning?


1 Answer 1


There are two possible sources: One is the article from the Bethesda Research Laboratories (reference 1), which names a few, the other is the book "DNA cloning: A practical approach" (see reference 2)., which sits here in my bookshelf.

Taking both together, the DH5 alpha strain is derived from the DH5 strain with the introduction of a few additional features. The naming DH are the initials of Douglas Hanahan which developed the strain. The strain is easy to transform with high efficency.

The new features of DH5 alpha are the recA and the endA1 mutations:

  • The endA1 mutation inactivates an intracellular endonuclease that degrades plasmid DNA.
  • The recA mutation eliminates homologous recombination. This reduces the chance for deletions and plasmid multimerization.

The DH5 strain also has the following features:

  • The hsdR17 mutation eliminates the restriction endonuclease of the EcoKI restriction-modification system, so DNA lacking the EcoKI methylation will not be degraded. DNA prepared from hsdR strains that are wt for hsdM will be methylated and can be used to transform wt E. coli K-12 strains.
  • Δ(lacZ)M15 is the alpha acceptor allele needed for blue-white screening with many lacZ based vectors.

Of special interest are the references 3 and 4, which gives you all the details you want to know.


  1. Bethesda Research Laboratories. 1986. BRL pUC host: E. coli DH5α competent cells. Focus 8(2):9. The article is on page 13 in this paper.
  2. DNA Cloning: A Practical Approach. Glover, D. M. (ed.), 1985, Vol. 1, p. 109, IRL Press, McLean, Virginia
  3. Choosing a Competent E.coli Strain
  4. E. coli genotypes
  • 1
    $\begingroup$ Oh, I've forgotten about it. Sorry! $\endgroup$
    – Analysis
    Commented Oct 16, 2014 at 15:53

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