Inference of admixed ancestry with Ancestry Informative Markers

Analysis of Ancestry Informative Markers (AIMs) is of interest to forensic geneticists for the purpose of assessing the origin of individuals. Often AIMs are used to produce investigative leads for potential suspects in crime cases and identification in missing persons mass disaster cases. We have previously suggested to assess the origin of the profile of interest by a likelihood ratio test on Fisher's exact test. The likelihood ratio test assesses the likelihood of the data under two competing hypotheses, where the null hypothesis assume common origin of the profile of interest and those in a specified population. However, in the case of a profile of an individual of admixed ancestry, there is an increased risk that the profile will be rejected in the constituting populations. The likelihood ratio test approach is extended by allowing for profile admixture implying the profile of interest is a mixture of profiles from two populations. The Expectation-Maximisation (EM) algorithm is used to handle the ambiguity of allocation of alleles at heterozygous markers. To demonstrate the approach, admixed profiles are simulated using AIMs genotypes in eight global meta populations.