Chulalongkorn Medical Journal


Background : In paternity testing, differences at genetic loci betweenthe alleged parent and the child would lead to the exclusion ofbiological paternity. Although rare, transmission inconsistent inpaternity testing or single mismatches in DNA profiles may occur,possibly due to either germline or somatic mutation. Whensingle locus discrepancy is present, the mutant allele ishypothesized that mutation occurs possibly in either father ormother.Objective : The objective of this paper is to report the mutation eventsrelated to many short tandem repeat (STR) loci that are frequentlyused and applied in various scenarios of forensic statistics.Design : A descriptive study.Setting : Forensic Serology and DNA, Department of Forensic Medicine,Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.Materials and Methods : In all, 11,280 meiosis transmissions from 630 paternity testingcases were investigated in Thai population from 2004 to 2010.Each locus was counted and analyzed as percentage ofmaternal or paternal mutation rate with 95% confidence interval.The mutation was described as the losses or gains of the repeatunits.Results : There were 24 mutations at 10 loci. The observed mutation ratewas ranged as 1.3 - 6.6 10-3(10 STR loci) per locus pergamete per generation. The mutation was more frequentlypresented in the paternal than the maternal germline.Conclusion : This is the preliminary study of mutation rate of STR loci observedin Thai population. The overall mutation rate is 1.9 10-3 perlocus per gamete per generation. This mutation information isuseful for forensic statistics to provide more accuracy STRcalculation results.


Faculty of Medicine, Chulalongkorn University

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