Linkage disequilibrium and historical effective population size in the Thoroughbred horse.
Abstract: Many genomic methodologies rely on the presence and extent of linkage disequilibrium (LD) between markers and genetic variants underlying traits of interest, but the extent of LD in the horse has yet to be comprehensively characterized. In this study, we evaluate the extent and decay of LD in a sample of 817 Thoroughbreds. Horses were genotyped for over 50,000 single nucleotide polymorphism (SNP) markers across the genome, with 34,848 autosomal SNPs used in the final analysis. Linkage disequilibrium, as measured by the squared correlation coefficient (r(2)), was found to be relatively high between closely linked markers (>0.6 at 5 kb) and to extend over long distances, with average r(2) maintained above non-syntenic levels for single nucleotide polymorphisms (SNPs) up to 20 Mb apart. Using formulae which relate expected LD to effective population size (N(e)), and assuming a constant actual population size, N(e) was estimated to be 100 in our population. Values of historical N(e), calculated assuming linear population growth, suggested a decrease in N(e) since the distant past, reaching a minimum twenty generations ago, followed by a subsequent increase until the present time. The qualitative trends observed in N(e) can be rationalized by current knowledge of the history of the Thoroughbred breed, and inbreeding statistics obtained from published pedigree analyses are in agreement with observed values of N(e). Given the high LD observed and the small estimated N(e), genomic methodologies such as genomic selection could feasibly be applied to this population using the existing SNP marker set.
© 2010 The Authors, Journal compilation © 2010 Stichting International Foundation for Animal Genetics.
Publication Date: 2010-11-26 PubMed ID: 21070270DOI: 10.1111/j.1365-2052.2010.02092.xGoogle Scholar: Lookup
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Summary
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The research article reveals the high extent of linkage disequilibrium (LD) in the Thoroughbred horse population and estimates its historical effective population size using over 50,000 single nucleotide polymorphism (SNP) markers. This comprehensive analysis informs of the potential for genomic methodologies such as genomic selection in this population.
Understanding the Research Focus
- The key focus of this research is the concept of linkage disequilibrium (LD), which essentially is a non-random association of alleles at different locations in a population’s genome. In simpler terms, it studies how variations in one part of the DNA sequence are associated with variations in another part.
- Besides, the research also emphasizes on the effective population size (Ne), which is a vital measure in population genetics which reflects the number of individuals in a population who contribute to the next generation.
- By exploring LD and Ne in Thoroughbred horses, the study aims to understand genetic variations better and inform genomic methodologies like genomic selection.
Methodology and Data Analysis
- The study involves 817 Thoroughbred horses, genotyped using over 50,000 single nucleotide polymorphism (SNP) markers. The final analysis incorporated 34,848 autosomal SNPs.
- Linkage disequilibrium was measured through the squared correlation coefficient (r(2)). Observations reveal high LD between closely linked markers and extended over long distances.
- The effective population size (Ne) was estimated considering a constant actual population size. Assessment of historical Ne was also done assuming linear population growth.
Insights and Conclusions
- The estimated Ne in the Thoroughbred population was found to be 100. The historical Ne suggested a decrease since the distant past, reaching a minimum twenty generations ago, followed by an increase until the present.
- The patterns observed in Ne align well with the known history of the Thoroughbred breed.
- Given the achieved levels of measured high LD and the small estimated Ne, the researchers affirm that genomic methodologies could feasibly be applied to this population using the existing SNP marker set.
Implications
- This research provides deep insights into the Thoroughbred horse’s genetic structure, contributing to genomic methodologies’ potential applications.
- Understanding the LD and Ne in this population can assist in more targeted breeding and conservation strategies for the Thoroughbred breed.
Cite This Article
APA
Corbin LJ, Blott SC, Swinburne JE, Vaudin M, Bishop SC, Woolliams JA.
(2010).
Linkage disequilibrium and historical effective population size in the Thoroughbred horse.
Anim Genet, 41 Suppl 2, 8-15.
https://doi.org/10.1111/j.1365-2052.2010.02092.x Publication
Researcher Affiliations
- Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin Biocentre, EH25 9PS, UK. laura.corbin@roslin.ed.ac.uk
MeSH Terms
- Animals
- Genetic Markers
- Genome-Wide Association Study
- Horses / genetics
- Linkage Disequilibrium
- Pedigree
- Population Density
Grant Funding
- BBS/E/D/05191133 / Biotechnology and Biological Sciences Research Council
Citations
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