Quantitative Genetics

by

Eleanor O'Brien, John Hunt, Jason B. Wolf

• LAST REVIEWED: 29 April 2015
• LAST MODIFIED: 29 April 2015
• DOI: 10.1093/obo/9780199941728-0064

Introduction

Quantitative genetics is the study of the genetic basis underlying phenotypic variation among individuals, with a focus primarily on traits that take a continuous range of values. Some familiar examples include height, weight, and longevity. However, traits that take discrete values (e.g., number of offspring) may also be analyzed within a quantitative genetics framework. “Threshold traits” are a special category of quantitative trait in which phenotypes take discrete, often binary, values (e.g., disease states) but reflect an underlying liability that has a continuous distribution, with different phenotypes produced above or below a certain threshold. Quantitative traits tend to be polygenic (influenced by a large number of genes) and also subject to nongenetic (environmental) influences. Heritability (H²), defined most generally as the proportion of the total phenotypic variation that is attributable to genetic factors (technically known as “broad sense” heritability), measures the relative importance of genes in determining phenotypic variance. “Narrow sense” heritability (h²) is the proportion of total phenotypic variation that is due to additive genetic variance and is of particular interest because of its importance in determining the response of a population to natural or artificial selection. Awareness of the factors underlying variation in quantitative traits is central to an understanding of evolution in natural populations and for predicting responses to selective breeding in agricultural species and disease risk in humans. Quantitative genetic variation has traditionally been studied using statistical analyses to partition components of phenotypic variation, often without knowledge of the genes involved. However, ongoing developments in genomic technology mean that it is increasingly possible to also identify the specific genes that underlie variation in quantitative traits.

General Overviews

The most widely used general textbooks on quantitative genetics are Falconer and Mackay 1996 and Lynch and Walsh 1998. Both offer an excellent introduction to quantitative genetics as well as providing a useful reference for more advanced researchers in the field. Roff 1997 is another useful textbook, differing from the others in that it is focused specifically on evolutionary concepts in quantitative genetics. Two very readable reviews of the theory and application of quantitative genetics are provided in Barton and Keightly 2002 and Hill 2010. A broad conceptual review of major issues in evolutionary quantitative genetics is provided in Roff 2007. A recent special issue of the journal Heredity (Walsh 2014) includes a collection of papers covering advances in quantitative genetics that have been facilitated by genomic, computational, and analytical developments. Mackay, et al. 2009 provides a timely forward looking perspective on the status of research into the genetic architecture of quantitative traits.

• Barton, Nicholas H., and Peter D. Keightly. 2002. Understanding quantitative genetic variation. Nature Reviews Genetics 3:11–21.

  DOI: 10.1038/nrg700

  Good review of the historical development of quantitative genetic theory. Has a particular emphasis on the identification of genes underlying quantitative genetic variation.

• Falconer, Douglas S., and Trudy F. C. Mackay. 1996. Introduction to quantitative genetics. 4th ed. Harlow, UK: Longmans Green.

  One of the best-known and most widely used general texts on quantitative genetics. It provides example problems and answers at the end of each chapter, making it a useful resource for teachers and students of quantitative genetics.

• Hill, William G. 2010. Understanding and using quantitative genetic variation. Philosophical Transactions of the Royal Society B 365:73–85.

  DOI: 10.1098/rstb.2009.0203

  In this review, Hill defines key terms, outlines the main assumptions of quantitative genetic analysis, and evaluates the consequences of recent genomic developments for estimating quantitative genetic parameters. He also touches on some vigorously debated topics in quantitative genetics, including missing heritability and maintenance of genetic variation in populations.

• Lynch, Michael, and Bruce Walsh. 1998. Genetics and analysis of quantitative traits. Sunderland, MA: Sinauer.

  This is a very comprehensive textbook on general concepts in quantitative genetics, covering both theory and the estimation of variance components using breeding designs. Useful reference for students and researchers at all levels.

• Mackay, Trudy F. C., Eric A. Stone, and Julien F. Ayroles. 2009. The genetics of quantitative traits: Challenges and prospects. Nature Reviews Genetics 10:565–577.

  DOI: 10.1038/nrg2612

  Provides a good introduction to approaches to studying the molecular genetic architecture of quantitative traits. Focuses on how the genomics revolution will allow us to dissect the connection between genotype and phenotype and, therefore, will allow us to begin to understand the molecular side of quantitative genetic variation.

• Roff, Derek A. 1997. Evolutionary quantitative genetics. New York: Chapman and Hall.

  DOI: 10.1007/978-1-4615-4080-9

  This textbook provides a basic introduction to fundamental principles in quantitative genetics and constitutes one of the most comprehensive overviews of evolutionary quantitative genetic concepts. It is a useful resource for advanced students and researchers.

• Roff, Derek A. 2007. A centennial celebration for quantitative genetics. Evolution 61.5: 1017–1032.

  DOI: 10.1111/j.1558-5646.2007.00100.x

  Published around the time of the one hundredth anniversary of the establishment of the field, this paper provides a general perspective on the major concepts in the field while also focusing specific attention on molecular approaches to studying variation (both QTL and analysis of specific genes).

• Walsh, Bruce, ed. 2014. Special issue: Advances in quantitative genetics. Heredity 112.1.

  DOI: 10.1038/hdy.2013.115

  Brings together a collection of papers detailing recent developments in quantitative genetics that have been facilitated by developments in genomic and analytical techniques, their application to ecological and evolutionary genetics, and breeding for improvement of crops and livestock.