The distribution of the effects of genes affecting quantitative traits in livestock

• Published in: Genetics selection evolution (Paris) Vol. 33; no. 3; pp. 209 - 229
• Main Authors: HAYES, Ben, GODDARD, Mike E
• Format: Journal Article
• Language: English; German
• Published: Les Ulis EDP Sciences 15.05.2001; BioMed Central Ltd; BioMed Central; BMC
• Subjects: Animal productions; Animals; Biological and medical sciences; Cattle - genetics; Chromosome Mapping; Classical genetics, quantitative genetics, hybrids; Dairying; distribution of gene effects; Fundamental and applied biological sciences. Psychology; Genes; Genetic aspects; Genetic Markers; genetic variance; Genetic Variation; Genetics of eukaryotes. Biological and molecular evolution; Heterozygote; Likelihood Functions; Livestock; Lod Score; marker assisted selection; Models, Genetic; Multifactorial traits; Physiological aspects; quantitative trait loci; Quantitative Trait, Heritable; Selection, Genetic; Swine - genetics; Terrestrial animal productions; Vertebrata; Vertebrates; Australia; Genetic mapping; Genetic marker; Quantitative character; Dairy cattle; Marker assisted selection; Genetic parameter; Gene expression; Metaanalysis; Pig; Gene effect; Quantitative genetics; Vertebrata; Mammalia; Genetic improvement; Artiodactyla; Ungulata
• ISSN: 0999-193X; 1297-9686; 1297-9686
• DOI: 10.1186/1297-9686-33-3-209

Meta-analysis of information from quantitative trait loci (QTL) mapping experiments was used to derive distributions of the effects of genes affecting quantitative traits. The two limitations of such information, that QTL effects as reported include experimental error, and that mapping experiments can only detect QTL above a certain size, were accounted for. Data from pig and dairy mapping experiments were used. Gamma distributions of QTL effects were fitted with maximum likelihood. The derived distributions were moderately leptokurtic, consistent with many genes of small effect and few of large effect. Seventeen percent and 35% of the leading QTL explained 90% of the genetic variance for the dairy and pig distributions respectively. The number of segregating genes affecting a quantitative trait in dairy populations was predicted assuming genes affecting a quantitative trait were neutral with respect to fitness. Between 50 and 100 genes were predicted, depending on the effective population size assumed. As data for the analysis included no QTL of small effect, the ability to estimate the number of QTL of small effect must inevitably be weak. It may be that there are more QTL of small effect than predicted by our gamma distributions. Nevertheless, the distributions have important implications for QTL mapping experiments and Marker Assisted Selection (MAS). Powerful mapping experiments, able to detect QTL of 0.1sigma(p), will be required to detect enough QTL to explain 90% the genetic variance for a quantitative trait.