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Updated: May 16, 2026

Infinium Assay for Large-scale SNP Genotyping Applications
Published on: November 19, 2013
Unexpected relationships and inbreeding in HapMap phase III populations
Eric L Stevens1, Joseph D Baugher, Matthew D Shirley
1Predoctoral Program in Human Genetics, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
This study reveals novel genetic relationships and inbreeding within the HapMap III dataset using identity-by-descent methods. Findings highlight potential biases in population genomics and inform future study designs.
Area of Science:
- Population Genomics
- Human Genetics
- Bioinformatics
Background:
- Accurate genetic relationship annotation is crucial for population genomics.
- Errors in relatedness data can introduce significant bias into studies.
- The HapMap Phase III dataset is a valuable resource for genetic analyses.
Purpose of the Study:
- To assess genetic relatedness within the HapMap Phase III data using identity-by-state (IBS) and identity-by-descent (IBD) methods.
- To identify novel pairwise relationships and instances of inbreeding.
- To evaluate the impact of discovered relationships on existing population genomic studies.
Main Methods:
- Analysis of HapMap Phase III data from 1,397 individuals across 11 ethnic populations.
- Application of identity-by-state (IBS) and identity-by-descent (IBD) statistical methods.
- Detection of identity-by-descent coefficients (K0, K1, K2) and regions of homozygosity (ROH).
Main Results:
- Confirmed previously identified unknown relatedness and discovered 1,657 novel pairwise relationships.
- Identified unexpected IBD1 values between known parents and IBD2 values in parent-child pairs.
- Detected regions of homozygosity (ROH) in offspring of related parents, inferring 28 inbred individuals.
- Found unexpected IBD0 and IBD2 values in several annotated relationships, suggesting errors or complex ancestry.
Conclusions:
- The study uncovers significant novel genetic relatedness and inbreeding within the HapMap III dataset.
- These findings underscore the potential for bias in previous population genomic studies.
- Recommendations are made for refining the design of future studies utilizing the HapMap Phase III resource.
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