Null allele sequence structure at the DYS448 locus and implications for profile interpretation
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Null alleles can occur with any PCR-based STR typing system. They generally are due to deletions within the target region or primer binding sites or by primer binding site mutations that destabilize hybridization of at least one of the primers flanking the target region. Although not common, null types were detected at the DYS448 locus in seven out of 1,005 unrelated males in the Hispanic population. Of these DYS448 null types, four individuals displayed an apparent duplication at the DYS437 locus. The additional allele observed at the DYS437 locus is in actuality a smaller-sized DYS448 amplicon, which is the result of a deletion of the invariant N42 base pair domain and downstream repeats within the DYS448 locus. Thus, some DYS448 null types are not truly null. A true DYS448 null allele carried numerous primer binding site variants and a large deletion including the N42 base pair domain and surrounding or downstream repeat regions. The presence of null alleles is not a real concern for interpretation of Y STR loci evidence; current methods for interpreting Y STR profiles easily accommodate such phenomena.
KeywordsY STRs Null alleles DYS448 DYS437 Sequencing Repeat motif Interpretation Statistics
- 29.Budowle B, Sinha SK, Lee HS, Chakraborty R (2003) Utility of Y-chromosome STR haplotypes in forensic applications. Forensic Sci Rev 15:153–164Google Scholar
- 30.Budowle B, Ge J, Chakraborty R (2007) Basic principles for estimating the rarity of Y-STR haplotypes derived from forensic evidence. Eighteenth International Symposium on Human Identification 2007. Promega Corporation, Madison, Wisconsin http://www.promega.com/ussymp18proc/default.htm Google Scholar