Biochemical Genetics, VoL 3i, Nos. 7/8, I993 DNA Isolation by a Rapid Method from Human Blood Samples: Effects of MgCI2, EDTA, Storage Time, and Temperature on DNA Yield and Quality Dcbomoy K. LahirP ,2 and Bill SchnabeP Received 5 Mar, 1993 Final 22 June 1993 The isolation of DNA from whole blood by a modified rapid method (RM) was tested using various detergents and buffer conditions. Extraction of DNA with either NP-40 or Triton X-IO0 gave a high yield of undegraded DNA in less than an hour. The concentration of magnesium ion in the buffers was critical to obtaining intact, high molecular weight (HMW) DNA. Greater than 10 mM MgCl2 led to degradation. Addition of EDTA to the buffer inhibits this degrada- tion. Preparation of DNA from blood stored at room temperature or incubated at 37~C for 24 hr resulted in the same amount and quality of DNA as from samples frozen at - 70°C. DNA from blood samples that had undergone more than four freeze-thaw cycles was found to be pal¢ially degraded. The modified RM can be applied to extract DNA from as little as 10 ixl of blood (340 ng of DNA) and from dried blood samples. DNA samples remained intact and undegraded for longer times when DNA was dissolved in higher concentrations of EDTA. KEY WORDS: high molecular weight DNA; MgClz; inte~ity of DNA; rapid method; DNA banking. INTRODUCTION The application of genetics to study human disease (Anderson, 1992; Miller, 1992) and to analyze gene function in vivo depends upon the quality of DNA samples. Intact and good-quality DNA is also essential for screening DNA This work was supported by grants from the Indiana Department of Mental Health and PHS RO1 AG10297. i Laboratory of Molecular Neurogenetics, Institute of Psychiatric Research, Department of Psychiatry, Indiana University School of Medicine, Indianapolis, Indiana 46202-4887. 2 To whom correspondence should be addressed at Laboratory of Molecular Neurogenetics, Institute of Psychiatric Research, Indiana University School of Medicine, 791 Union Drive, Indianapolis, Indiana 46202-4887. 321 0006-2928/93/0800-0321507.00/0 ©i993Plenum Publishing Corporation