- Identification and characterization of variant Allele 34.1 at short tandem repeat (STR) locus D21s11

Abstract

D21S11 is one of the core short tandem repeat (STR) locus included in most
of the commercial kits used for DNA parentage testing, kinship analysis and
human identification purpose. It is a complex tetranucleotide repeat located on
the long arm of chromosome 21 which surrounds a constant 43 bp section. The
allele designation of a particular locus is correctly assigned by comparing the
alleles with an allelic ladder that consists of all possible alleles at that particular
locus. In this study we observed a variant allele at D21S11 during a routine
paternity test while typing the putative father. The variant allele was called by
the Genotyper™ software as 34.1, though this allele was not included in the
allelic ladder provided by the manufacturer. Sequencing analysis revealed that
the variant allele was generated as a change in the repeat motif (TCTA) for TCA
at the 3 end of the repeat region. This variant allele was first reported in
Bangladeshi population from our laboratory in a previous report. This study
involves further characterization of the reported allele by means of direct DNA
sequencing of the D21S11 locus.