Interpreting DNA Mixtures in Structured Populations

Abstract

DNA profiles from multiple-contributor samples are interpreted by comparing the probabilities of the profiles under alternative propositions. The propositions may specify some known contributors to the sample and may also specify a number of unknown contributors. The probability of the alleles carried by the set of people, known or unknown, depends on the allelic frequencies and also upon any relationships among the people. Membership of the same subpopulation implies a relationship from a shared evolutionary history, and this effect has been incorporated into the probabilities. This acknowledgment of the effects of population structure requires account to be taken of all people in a subpopulation who are typed, whether or not they contributed to the sample.

Object-oriented Bayesian networks for paternity cases with allelic dependencies

“…If we then divide the percentages (81.10 by 18.90) we obtain the paternity index value, 4.29. Evett and Weir [6] show the following is the PI formula for this case, (5) When θ = 0.03 and p 2 = 0.1, this formula gives PI = 4.29 which corresponds to HUGIN's result.…”

“…A body of evidence can be evaluated by calculating a likelihood ratio [5]: (1) where E denotes the evidence, H p and H d denote the plaintiff's and defendant's hypotheses, respectively. In paternity cases, the likelihood ratio is termed the paternity index, or PI.…”

“…This term, denoted here by θ, is commonly referred to as the inbreeding or coancestry coefficient [5]. It is usually not possible to specify an exact θ value for a given case, as estimation requires data from more than one subpopulation.…”

Detecting multiple DNA human profile from a mosquito blood meal

“…The DNA Mix v. 3.2 software was used for the statistical analysis to calculate the likelihood ratios (Curran et al, 1999) of the sample mixture with genetic profiles. An ancestry coefficient of 0.01 and minimum frequency of 0.01 was used in a database of allelic frequencies of a Brazilian population (Aguiar et al, 2012) with a confidence interval of 95%.…”

Statistical Analysis of Forensic Dna: Computational Problems Solved and to Be Solved

“…Based on genetic and statistical justification, Balding and Nichols (1994) showed that, in general, if there are y alleles of AZ observed among n alleles, then the probability that the next allele is an AZ is (4) This formula can also be obtained if a state of evolutionary equilibrium has been established (Wright, 1951;Curran et al, 1999).…”