UW Aquatic & Fishery Sciences Quantitative Seminar

Elizabeth Thompson

UW, Statistics

Variance in and inference of coancestry, in relatives and over genomes

Gene identity by descent (ibd) underlies all similarities among relatives, and conversely the patterns of gene identity by descent we can infer provide information about relationships among individuals. However, the process of meiosis that leads to sharing of genome among relatives also leads to high variance in proportion of genome shared by relatives. Due to genetic linkage, genomes are quite short from the perspective of estimating relationships. We discuss whether pedigrees are useful in the inference of shared genome, and whether inferred ibd is useful in inferring relationships.

We also outline a model for the inference of ibd genome among individuals not known to be related, or in the absence of pedigree information. The time-depth of this ibd is of the order of 10's of generations. Linkage disequilibrium (LD) tends to confound such inferences, since LD is also a reflection of the relationship structure of the population and of remote coancestry among individuals on the scale of 100's of generations. We present results of a recent simulation study of the performance of our inference approach, and of the impact of LD in the population on the ability to detect segments of ibd that result from more recent coancestry.