|
To understand the mutational patterns and mechanism of short tandem repeats (STRs), 160 familial identification positive cases were checked by PAGE & silver stain. Mutations were observed in the 7 families at 6 STR loci (4 in autosomal STR loci and 2 in Y-STR loci). Alleles of each case observed mutation were re-amplified by PCR, and cloned. Each allele was sequenced by ABI 310 sequencer. There were 6 out of 7 pedigrees in which the ’new’alleles gained or lost a single repeat unit (4 gains, 2 losses). Only one pedigree (case 5-DYS464) gains one new allele. Double step mutations event or more than were not occurred. In the 5 pedigrees (autosomal locus), there were 3 pedigrees whose ’new’alleles came from fathers, 1 from mothers, 1 from either father or mother. The ratio was 4 : 1 or 3 : 2 between fathers and mothers. The mutation of 7 STR loci, except for case 4-DYS 448 (’AGAGAT’in DYS464), occurred in the long, uninterrupted tetranucleotide repeat regions ( ’AGAT’& ’AGAC’in D12S391, ’AAAG’in ACTBP2, ’ATAG’in D19S253, ’CCTT’in DYS464 and ’CTTT’in FGA). Father’s age seems not to be related to occurrence of mutation event. The features of mutation in STR loci are important in forensic application such as the definition of criteria for exclusion in kinship identification case and the interpretation of DNA profiles in identification analysis.
|