Criteria for Selecting Microhaplotypes: Mixture Detection and Deconvolution

• NCJ Number: 310121
• Journal: Investigative Genetics Volume: 6 Issue: 1 Dated: January 2015
• Author(s): Kenneth K. Kidd; William C. Speed
• Date Published: January 2015
• Length: 10 pages
• Grant Number(s): 2013-DN-BX-K023; 2010-DN-BX-K225
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical)

Annotation

In this paper, researchers establish criteria for selecting microhaplotypes.

Abstract

In this study, researchers establish a criteria for selecting microhaplotypes through mixture detection and deconvolution. The researchers find that 3-SNP microhaplotypes will sometimes meet this criterion, but 4-SNP microhaplotypes can even exceed this criterion and have values >4. The expectations for the ability to qualitatively detect mixtures are given for different integer values of A_e, and the cumulative probabilities of detecting mixtures based on testing multiple microhaps are shown to exceed 95% with as few as five loci with average A_e values of even slightly greater than 3.0. Microhaplotypes with A_e values of >3 will be exceedingly useful in ordinary forensic practice. The authors define a microhaplotype to be a locus with two or more single nucleotide polymorphisms (SNPs) that occur within a short segment of DNA (e.g., 200 bp) that can be covered by a single sequence run and collectively define a multiallelic locus. When all alleles are equally frequent, the probability of detecting three or more alleles in a mixture is at maximum. The classical population genetics concept of effective number of alleles at a locus, termed A_e, converts the unequal allele frequencies at a locus into a value that is equivalent to some number of equally frequent alleles, allowing microhaplotype loci to be ranked. Microhaplotypes can be highly informative for many forensic questions, including detection of mixtures of two or more sources in a DNA sample, a common problem in forensic practice. (Published Abstract Provided)