Abstract
An overwhelming amount of genetics that is taught in classrooms is derived from a common assumption, which is that a given phenotype is the output of a given gene. This one gene-one phenotype assumption actually does not hold true for the majority of phenotypic traits. Most of the traits that you would have studied till now can be classified as qualitative traits. They encompass different types or kinds of a trait. For example, curly hair, wavy hair and straight hair are different kinds of qualities of hair. Similarly, red or white eye colour in Drosophila refers to a qualitative trait, the quality in question being the colour. Other examples include human blood-group types (A, B, AB and O) and the shape of the fruit in squash (spherical, disc-shaped, elongated, etc.). However, careful observation of the world around us informs us that a given trait can be given a numerical value (or a unique phenotypic class), and these numerical values tend to be part of a range of possible degrees and intensity of the trait in question. For example, the protein content in a seed will have a numerical value, and these values are going to vary even for seeds of plants of the same species. Thus, protein content of a seed is a typical quantitative trait. Such traits are also called continuous traits to distinguish them from traits that can be categorized in a few phenotypic classes. The latter traits are known as discontinuous traits. The tall and dwarf pea plants of Mendel are considered to be discontinuous traits. However, we can also study the range of tallness or dwarfness of these plants and analyse it quantitatively. Therefore, a given qualitative trait can sometimes be further studied quantitatively. Human IQ scores are also considered to be a quantitative trait.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Similar content being viewed by others
References
Arranz JJ, Coppieters W, Berzi P, Cambisano N, Grisart B, Karim L, Marcq F, Moreau L, Mezer C, Riquet J, Simon P (1998) A QTL affecting milk yield and composition maps to bovine chromosome 20: a confirmation. Anim Genet 29:107–115
Bidinost F, Roldan DL, Dodero AM, Cano EM, Taddeo HR, Mueller JP, Poli MA (2008) Wool quantitative trait loci in merino sheep. Small Rumin Res 74:113–118
Grisart B, Coppieters W, Farnir F, Karim L, Ford C, Berzi P, Cambisano N, Mni M, Reid S, Simon P, Spelman R (2002) Positional candidate cloning of a QTL in dairy cattle: identification of a missense mutation in the bovine DGAT1 gene with major effect on milk yield and composition. Genome Res 12:222–231
Gutiérrez-Gil B, El-Zarei MF, Alvarez L, Bayón Y, De La Fuente LF, San Primitivo F, Arranz JJ (2009) Quantitative trait loci underlying milk production traits in sheep. Anim Genet 40:423–434
Liu Z, Sun C, Yan Y, Li G, Wu G, Liu A, Yang N (2018) Genome-wide association analysis of age-dependent egg weights in chickens. Front Genet 9
Roldan DL, Dodero AM, Bidinost F, Taddeo HR, Allain D, Poli MA, Elsen JM (2010) Merino sheep: a further look at quantitative trait loci for wool production. Animal 4:1330–1340
Russell PJ (2014) iGenetics, a molecular approach, 3rd edn. Pearson New International Edition, Harlow
Shorter J, Couch C, Huang W, Carbone MA, Peiffer J, Anholt RR, Mackay TF (2015) Genetic architecture of natural variation in Drosophila melanogaster aggressive behavior. Proc Natl Acad Sci 112:E3555–E3563
Sinha NK, Singh SK (1997) Genetic and phenotypic parameters of body weights, average daily gains and first shearing wool yield in Muzaffarnagri sheep. Small Rumin Res 26:21–29
Snustad DP, Simmons MJ (2012) Principles of genetics, 6th edn. John Wiley and Sons, Inc., Hoboken, NJ
Vesely JA, Peters HF, Slen SB, Robison OW (1970) Heritabilities and genetic correlations in growth and wool traits of Rambouillet and Romnelet sheep. J Anim Sci 30:174–181
Wolc A, Arango J, Settar P, Fulton JE, O’sullivan NP, Preisinger R, Habier D, Fernando R, Garrick DJ, Hill WG, Dekkers JCM (2012) Genome-wide association analysis and genetic architecture of egg weight and egg uniformity in layer chickens. Anim Genet 43:87–96
Yuan J, Sun C, Dou T, Yi G, Qu L, Qu L, Wang K, Yang N (2015) Identification of promising mutants associated with egg production traits revealed by genome-wide association study. PLoS One 10:e0140615
Zhang Q, Boichard D, Hoeschele I, Ernst C, Eggen A, Murkve B, Pfister-Genskow M, Witte LA, Grignola FE, Uimari P, Thaller G (1998) Mapping quantitative trait loci for milk production and health of dairy cattle in a large outbred pedigree. Genetics 149:1959–1973
Further Reading
Falconer DS, Mackay TFC (1996) Introduction to quantitative genetics, 4th edn. Addison Wesley Longman Limited, Harlow
Griffiths AJ, Wessler SR, Lewontin RC, Gelbart WM, Suzuki DT, Miller JH (2011) An introduction to genetic analysis, 10th edn. W H Freeman and Company, New York
Klug WS, Cummings MR, Spencer CA, Palladino MA (2012) Concepts of genetics, 10th edn. Pearson Education, Inc., San Francisco, CA
Lynch M, Walsh B (1998) Genetics and analysis of quantitative traits. Sinauer Associates, Inc., Sunderland, MA
Pierce BA (2010) Genetics: a conceptual approach. W H Freeman and Company, New York
Powar CB (2003) Genetics (volume 1), 1st edn. Himalaya Publishing House, Mumbai
Singh BD (2005) Genetics, 1st edn. Kalyani Publishers, New Delhi
Tamarin RH (2001) Principles of genetics, 7th edn. The McGraw-Hill Companies, New York
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2022 The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
About this chapter
Cite this chapter
Chatterjee, A. (2022). Quantitative Genetics. In: Kar, D., Sarkar, S. (eds) Genetics Fundamentals Notes. Springer, Singapore. https://doi.org/10.1007/978-981-16-7041-1_20
Download citation
DOI: https://doi.org/10.1007/978-981-16-7041-1_20
Published:
Publisher Name: Springer, Singapore
Print ISBN: 978-981-16-7040-4
Online ISBN: 978-981-16-7041-1
eBook Packages: Biomedical and Life SciencesBiomedical and Life Sciences (R0)