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. 2015 Mar 7:16:23.
doi: 10.1186/s12863-015-0179-y.

ALDsuite: Dense marker MALD using principal components of ancestral linkage disequilibrium

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ALDsuite: Dense marker MALD using principal components of ancestral linkage disequilibrium

Randall C Johnson et al. BMC Genet. .

Abstract

Background: Mapping by admixture linkage disequilibrium (MALD) is a whole genome gene mapping method that uses LD from extended blocks of ancestry inherited from parental populations among admixed individuals to map associations for diseases, that vary in prevalence among human populations. The extended LD queried for marker association with ancestry results in a greatly reduced number of comparisons compared to standard genome wide association studies. As ancestral population LD tends to confound the analysis of admixture LD, the earliest algorithms for MALD required marker sets sufficiently sparse to lack significant ancestral LD between markers. However current genotyping technologies routinely provide dense SNP data, which convey more information than sparse sets, if this information can be efficiently used. There are currently no software solutions that offer both local ancestry inference using dense marker data and disease association statistics.

Results: We present here an R package, ALDsuite, which accounts for local LD using principal components of haplotypes from surrogate ancestral population data, and includes tools for quality control of data, MALD, downstream analysis of results and visualization graphics.

Conclusions: ALDsuite offers a fast, accurate estimation of global and local ancestry and comes bundled with the tools needed for MALD, from data quality control through mapping of and visualization of disease genes.

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Figures

Figure 1
Figure 1
Hidden Markov Model for ancestry inference. Each individual’s local ancestral state probability, γ, is modeled as a function of preceding ancestral state probabilities in each Markov chain, genetic distance to neighboring markers, d, individual global ancestry parameters and observed haplotype or genotypes, a, in a region
Figure 2
Figure 2
Representative chromosomes from one individual in the ASW population. Local ancestry inference along chromosome 20 is shown for ALDsuite (top), PCAdmix (middle) and MULTIMIX (bottom). A stacked bar plot indicating the inferred probability of African ancestry (represented by green bars) and European ancestry (represented by blue bars) is given for each phased haplotype. The width of each bar is proportional to the window size (in cM) covered by the markers used to infer ancestry

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