Computation of allelic frequencies using the “Cerberus” beowulf cluster

Abstract

Short Tandem Repeats (STR) are specific repeats of a sequence of four or more nucleotides with no breaks in it (e.g. ATAGATAGATAGATAG where ‘ATAG’ is the repeating sequence). In criminal investigations involving biological evidence, the FBI recognizes 13 core loci (specific areas on chromosomes where STRs are most commonly found) where usually one or two alleles exist for every individual [1]. These 13 loci are organized in a table form, called an Allele Panel, showing the locus analyzed and the number of paternal and maternal STRs that are present in each. However, in some criminal and anthropological cases, more than two alleles may present themselves in any allele of a panel. This can be problematic, since one particular individual should only have one or two STRs per allele (one inherited from their father and one inherited from their mother). If 3 or more STRs are present, for example, minimally 3 or more subjects' DNA is being analyzed. This sort of mixture can occur by contamination from the scientist(s) testing the sample or by the presence of DNAs from multiple individuals.