Sue Seim, Linda Wiessner, Tami Maus and Patrick Williams
Memorial Blood Center of Minnesota, Minneapolis, MN

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Over a period of two years, 20,445 blood specimens have been analyzed for two VNTR loci, D12S11 and D17S79, for the purpose of parentage determination. Using the restriction enzyme Pst I, with alkaline phosphotase labeled probes, followed by a colorimetric detection system, 8 specimens exhibited a 3 banded pattern and 2 showed 4 bands. Five such patterns were observed with D12S11 and five with D17S79. Results of all tests were confirmed by subsequent repeat testing using newly extracted DNA to eliminate the possibility of sample contamination. Quality and quantity of DNA was assured through standard spectrophotometric (A260/A280) measurements. Completeness of restriction by Pst I enzyme was demonstrated by post electrophoresis ethidium bromide staining. Multibanded patterns were uniform in intensity. Testing with additional RFLP systems was performed in these cases where such patterns occurred to resolve paternity issues. It was noted that 8 of 10 specimens showing these unusual banding patterns came from persons listing their race as black. Since 25% of all specimens tested in this laboratory are from blacks, this makes the multibanded occurrence in this population disproportionately high. These multibanded patterns might be explained by Mendelian inherited translocations occurring at the distal tip of chromosomes 12 and 17 (12q24.3 and 17q25) rather than point mutations resulting in additional restriction sites and/or probe sites.