Molecular characterization and Austrian Caucasian population data of the multi-copy Y-chromosomal STR DYS464.

DYS464 is a multi-copy STR system with four positions on the Y-chromosome (DYS464a, b, c, and d) which was recently identified and characterized [Forensic Sci. Int. 130 (2002) 97]. The aims of our study were to perform a population study, to estimate the mutation rate and an extensive sequence analysis in order to confirm the nomenclature. Fourteen different alleles were found in an Austrian population sample with an allele length varying from 9 to 19 repeats. All alleles were cloned and sequenced. Alleles 9-19 showed the general repeat structure (CCTT)n...(CCTT)2...(CCTT)3...(CCTT)4...(CCTT)2...(CCTT)2. The nomenclature is based on the number of repeated units of the variable (CCTT)n-stretch only. In 13% of the samples intermediate alleles, namely 14.3A, 14.3B and 15.3 were detected. In these alleles the variable repeat block is interrupted by a CTT motif (14.3A: (CCTT)3CTT(CCTT)11; 14.3B and 15.3: (CCTT)7CTT(CCTT)7/8). A comparison with GenBank entries revealed the existence of a length variant due to a deletion of one cytosine in the 5' flanking region of the first repeat block. We designed an alternative forward primer to circumvent possible ambiguities in the allele designation. A total of 54 different genotypes were identified in 135 men corresponding to a discrimination capacity (DC) of 40% and a gene diversity (GD) of 0.97. These values are much higher than those of other Y-chromosomal short tandem repeats (Y-STRs). DYS464 has the same haplotype diversity (HD) as the combination of the five Y-STR loci with the lowest gene diversities of the Y-STR core set. On the other hand, a combination of the three most diverse loci (DYS464, DYS385 and DYS390) has the same capacity to distinguish between paternal lineages than the complete minimal haplotype (minHT) consisting of eight Y-STR loci. In our population sample the addition of DYS464 to the minHT increases the number of different haplotypes from 110 to 122. The mutation-rate estimate based on the 70 meioses analyzed amounts to 2.86 x 10(-2) (95% confidence interval 3.5 x 10(-3) to 9.95 x 10(-2)). This value is approximately 10 times higher than the average mutation-rate estimate for Y-STRs.