Studies on DNA extracted from postmortem tissues

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1. DNA extracted from various postmortem tissues up to 24 hours after death was analyzed using a multi-locus probe, MZ 1.3 (MZ). DNA from lungs showed the most prominent band patterns. DNA from spleen, kidneys and muscles also showed prominent band patterns, whereas DNA from blood, liver and pancreas was found to be not suitable for DNA fingerprinting because of rapid degradation of high-molecular-weight DNA.2.When DNA was extracted monthly from muscle specimens which were frozen at -20ﾟC, a steady decline of the yields of DNA was observed in relation to frozen periods. When DNA extracted from muscles was preserved at 4ﾟC, the decline of the yields was not observed.3. DNA was extracted daily from small strips of muscles that were stored at +20ﾟC in moist chambers. The yields of DNA steadily decreased up to first 3-6 days. Subsequently, the yields gradually increased. However, the fragment patterns of MZ could not be detected in DNA from muscles stored for more than 3 days. This mnay in part be explained by the degradation of human genomic DNA and its substitution by genomic DNA of microorganisms.4. DNA which was extracted from several bacteria was digested with a restrictoin enzyme and analyzed using MZ.DNA from some bacteria could not be digested completely and DNA from the other bacteria showed wider and fainter bands which could clearly be distinguished from the human hypervariable fragment patterns.5. When DNA was extracted from the same specimens by using various procedures, DNA of sufficient quantity an quality was obtained by a saturated NaCl method, a liquid nitrogen method and a dry ice method as well as by a usual phenol-chloroform method. The band patterns were almost identical regardless of the extraction methods.