No abstract

No abstract

No abstract

Three sampled populations of unrelated males--African American, Caucasian, and Hispanic, all from Texas-were typed for 16 Y short tandem repeat (STR) markers using the AmpFlSTR Yfiler kit. These samples also were typed previously for the 13 core CODIS autosomal STR loci. Most of the 16 marker haplotypes (2478 out of 2551 distinct haplotypes) were observed only once in the data sets. Haplotype diversities were 99.88%, 99.89%, and 99.87% for the African American, Caucasian, and Hispanic sample populations, respectively. F(ST) values were very small when a haplotype comprised 10-16 markers. This suggests that inclusion of substructure correction is not required. However, haplotypes consisting of fewer loci may require the inclusion of F(ST) corrections. The testing of independence of autosomal and Y STRs supports the proposition that the frequencies of autosomal and Y STR profiles can be combined using the product rule.

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.