title: Reconciling the analysis of IBD and IBS in complex trait studies.
abstract: Identity by descent (IBD) is a fundamental concept in genetics and refers to alleles that are descended from a common ancestor in a base population. Identity by state (IBS) simply refers to alleles that are the same, irrespective of whether they are inherited from a recent ancestor. In modern applications, IBD relationships are estimated from genetic markers in individuals without any known relationship. This can lead to erroneous inference because a consistent base population is not used. We argue that the purpose of most IBD calculations is to predict IBS at unobserved loci. Recognizing this aim leads to better methods to estimating IBD with benefits in mapping genes, estimating genetic variance and predicting inbreeding depression.
authors.affiliation: Queensland Statistical Genetics Laboratory, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, Queensland 4006, Australia. Peter.Visscher@qimr.edu.au
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Powell
authors.forename: Peter M
authors.initials: PM
authors.lastname: Visscher
authors.forename: Michael E
authors.initials: ME
authors.lastname: Goddard
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000235:genetics; D014644:Genetic Variation / Q000502:physiology*; D005828:Genetics, Population; D006801:Humans; D007178:Inbreeding; D008954:Models, Biological; D008957:Models, Genetic; D010375:Pedigree; D040641:Quantitative Trait Loci / Q000235:genetics; D019655:Quantitative Trait, Heritable