Estimating Identity by Descent Among Multiple Individuals in Populations

• Activity Number: 528
• Type: Contributed
• Date/Time: Wednesday, August 1, 2012 : 10:30 AM to 12:20 PM
• Sponsor: WNAR
• Author(s): Christopher Glazner*+ and Elizabeth Alison Thompson
• Companies: University of Washington and University of Washington
• Keywords: identity by descent ; population genetics

Abstract

Individuals not known to be related may share some segments of their genomes identical by descent (IBD) due to shared ancestry in the recent past. Detection of these segments can aid in disease mapping when a rare causal variant is unprobed, or if multiple variants in a region cause the same disease. The IBD between a pair of individuals can be estimated from dense marker data using a Hidden Markov Model (HMM) which describes the transitions among IBD states along the chromosome. Pairwise inferences can be used in some analyses, but the full IBD configuration among all individuals contains more information. We propose to obtain joint IBD estimates among many individuals by sampling from the forward probabilities of the HMM conditionally on IBD between other pairs. The sampled IBD configurations are equivalence relations on the entire group, which may not be the case if pairwise inferences are naively combined, and reflect the dependence between markers. These realizations may then be used for further analysis, such as a case-control comparison.