Quantitative genetics

Quantitative genetics is the study of quantitative traits, which are phenotypes that vary continuously—such as height or mass—as opposed to phenotypes and gene-products that are discretely identifiable—such as eye-colour, or the presence of a particular biochemical.

Both of these branches of genetics use the frequencies of different alleles of a gene in breeding populations (gamodemes), and combine them with concepts from simple Mendelian inheritance to analyze inheritance patterns across generations and descendant lines. While population genetics can focus on particular genes and their subsequent metabolic products, quantitative genetics focuses more on the outward phenotypes, and makes only summaries of the underlying genetics.

Due to the continuous distribution of phenotypic values, quantitative genetics must employ many other statistical methods (such as the effect size, the mean and the variance) to link phenotypes (attributes) to genotypes. Some phenotypes may be analyzed either as discrete categories or as continuous phenotypes, depending on the definition of cut-off points, or on the metric used to quantify them.^[1]^: 27–69 Mendel himself had to discuss this matter in his famous paper,^[2] especially with respect to his peas' attribute tall/dwarf, which actually was derived by adding a cut-off point to "length of stem".^[3]^[4] Analysis of quantitative trait loci, or QTLs,^[5]^[6]^[7] is a more recent addition to quantitative genetics, linking it more directly to molecular genetics.

^ Anderberg, Michael R. (1973). Cluster analysis for applications. New York: Academic Press.
^ Mendel, Gregor (1866). "Versuche über Pflanzen Hybriden". Verhandlungen Naturforschender Verein in Brünn. iv.
^ Mendel, Gregor (1891). "Experiments in plant hybridisation". J. Roy. Hort. Soc. (London). XXV. Translated by Bateson, William: 54–78.
^ The Mendel G.; Bateson W. (1891) paper, with additional comments by Bateson, is reprinted in: Sinnott E.W.; Dunn L.C.; Dobzhansky T. (1958). "Principles of genetics"; New York, McGraw-Hill: 419-443. Footnote 3, page 422 identifies Bateson as the original translator, and provides the reference for that translation.
^ A QTL is a region in the DNA genome that effects, or is associated with, quantitative phenotypic traits.
^ Watson, James D.; Gilman, Michael; Witkowski, Jan; Zoller, Mark (1998). Recombinant DNA (Second (7th printing) ed.). New York: W.H. Freeman (Scientific American Books). ISBN 978-0-7167-1994-6.
^ Jain, H. K.; Kharkwal, M. C., eds. (2004). Plant Breeding - Mendelian to molecular approaches. Boston Dordecht London: Kluwer Academic Publishers. ISBN 978-1-4020-1981-4.

[Anderberg_1973-1] Anderberg, Michael R. (1973). Cluster analysis for applications. New York: Academic Press.

[Mendel-2] Mendel, Gregor (1866). "Versuche über Pflanzen Hybriden". Verhandlungen Naturforschender Verein in Brünn. iv.

[Mendel_Bateson-3] Mendel, Gregor (1891). "Experiments in plant hybridisation". J. Roy. Hort. Soc. (London). XXV. Translated by Bateson, William: 54–78.

[4] The Mendel G.; Bateson W. (1891) paper, with additional comments by Bateson, is reprinted in: Sinnott E.W.; Dunn L.C.; Dobzhansky T. (1958). "Principles of genetics"; New York, McGraw-Hill: 419-443. Footnote 3, page 422 identifies Bateson as the original translator, and provides the reference for that translation.

[5] A QTL is a region in the DNA genome that effects, or is associated with, quantitative phenotypic traits.

[W&G&W&Z_1998-6] Watson, James D.; Gilman, Michael; Witkowski, Jan; Zoller, Mark (1998). Recombinant DNA (Second (7th printing) ed.). New York: W.H. Freeman (Scientific American Books). ISBN 978-0-7167-1994-6.

[J&K_2004-7] Jain, H. K.; Kharkwal, M. C., eds. (2004). Plant Breeding - Mendelian to molecular approaches. Boston Dordecht London: Kluwer Academic Publishers. ISBN 978-1-4020-1981-4.

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