Isolation of DNA Fragments for Microinjection

  • Duncan R. Smith
  • David Murphy
Part of the Methods in Molecular Biology™ book series (MIMB, volume 18)


The purification of a DNA fragment for microinjection is extremely important. This chapter describes a rapid and efficient technique for isolating specific DNA fragments from agarose gels run in Tris-acetate buffer, and was first described by Vogelstein and Gillespie (1). Agarose blocks containing the DNA fragment of interest are cut from gels and dissolved in NaI, a chaotropic salt that at concentrations of around 4M is able to solubilize agarose. Glass beads are then added, which, in this concentration of NaI, efficiently bind to the released DNA fragments. RNA, proteins, and other impurities fail to bind to the glass fragments. Following a few washing cycles, the purified DNA is eluted from the glass into a low-salt buffer. This method produces DNA of sufficient purity for most applications. No further purification is needed for the DNA fragment to be subcloned, labeled using standard methods, or recleaved by restriction endonucleases. However, further purification is recommended if the DNA is to be microinjected into fertilized one-cell eggs. Passage through a Sephadex G-50 column previously equilibrated in MiTE removes all contaminating solutes and solvents (e.g., ethanol) that might be deleterious to the egg. Filtration through the 0.45/gmm filter removes particulate matter that might block the microinjection pipet.


Glass Bead Glass Fragment Ethanol Wash Occasional Agitation Agarose Block 
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  1. 1.
    Vogelstein, B. and Gillespie, D. (dy1979) Preparative and analytical purification of DNA from agarose. Proc. Natl. Acad. Sci USA 76, 615–619PubMedCrossRefGoogle Scholar
  2. 2.
    Brinster, R L, Chen, H Y, Trumbauer, M E, Yagle, M. K., and Palmiter, R. D (1985) Factors affecting the efficiency of introducing foreign DNA into mice by microinjecting eggs. Proc. Natl. Acad. Sci USA 82, 4438–4442.PubMedCrossRefGoogle Scholar

Copyright information

© Humana Press Inc., Totowa, NJ 1993

Authors and Affiliations

  • Duncan R. Smith
    • 1
  • David Murphy
    • 2
  1. 1.Molecular Neurobiology Laboratory, Institute of Molecular and Cell BiologyNational University of SingaporeRepublic of Singapore
  2. 2.Neuropeptide Laboratory, Institute of Molecular and Cell BiologyNational University of SingaporeRepublic of Singapore

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