# Complex segregation analysis > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Complex_segregation_analysis > Markdown URL: https://mediated.wiki/source/Complex_segregation_analysis.md > Source: https://en.wikipedia.org/wiki/Complex_segregation_analysis > Source revision: 1240736799 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) '''Complex segregation analysis ''' ('''CSA''') is a technique within [genetic epidemiology](/source/genetic_epidemiology) to determine whether there is evidence that a major [gene](/source/gene) underlies the distribution of a given [phenotypic](/source/phenotypic) trait. CSA also provides evidence to whether the implicated trait is inherited in a [Mendelian](/source/Mendelian) [dominant](/source/Dominance_(genetics)), [recessive](/source/recessive), or [codominant](/source/codominance) manner. ==Purpose of CSA== CSA is often a preliminary step in genetic epidemiology. The purpose of CSA is to provide initial evidence that a single gene has a major effect on a particular phenotypic trait. Only phenotypic information, not [genotypic](/source/genotype) information, is required for CSA. CSA can provide evidence, but not definitively prove a trait is under the control of a single gene. Evidence from CSA studies can be used to justify which phenotypes might be appropriate for more in-depth studies such as [linkage](/source/genetic_linkage) analysis.{{cite journal | author = Elston R | title = Segregation and linkage analysis. | journal = Animal Genetics | volume = 23 | issue = 1| pages = 59–62| year = 1992 | pmid = 1570893 | doi = 10.1111/j.1365-2052.1992.tb00232.x}} ==Study design and data analysis== CSA requires phenotypic information on family members in a [pedigree](/source/pedigree_chart). A variety of [models](/source/conceptual_model) with different parameters and assumptions about the nature of the [inheritance](/source/heredity) of the trait are fit to the data. CSA studies may include non-genetic models which assume the trait has no genetic component and is only determined by [environmental](/source/environment_(biophysical)) factors, models which include environmental components as well as multi-gene [heritability](/source/heritability) components, and models which include environment, multi-gene heritability, and a single major gene to best fit the data.{{cite journal | author = Jarvik G | title = Complex segregation analyses: uses and limitations. | journal = American Journal of Human Genetics | volume = 63 | issue = 4| pages = 931–4 |date=October 1998 | pmid = 9758633 | doi = 10.1086/302075| pmc=1377507}} CSA software uses a [maximum likelihood](/source/maximum_likelihood) estimator to assign the best fitting [coefficients](/source/coefficients) to each component in all models. Nested models are then tested for their [goodness of fit](/source/goodness_of_fit) starting at the most complex. If two models are found to fit equally well, the more complex model is rejected in favor of the simpler model. If the best fitting model includes a single major gene component, there is evidence that the trait of interest is under Mendelian control. ==Examples of publications using CSA== * {{cite journal |vauthors=Schumacher MC, Hasstedt SJ, Hunt SC, Williams RR, Elbein SC | title = Major gene effect for insulin levels in familial NIDDM pedigrees. | journal = Diabetes | volume = 41 | issue = 4| pages = 416–23| year = 1992 | pmid = 1607068 | doi = 10.2337/diabetes.41.4.416}} * {{cite journal |vauthors=Pairitz G, Davignon J, Mailloux H, Sing CF | title = Sources of interindividual variation in the quantitative levels of apolipoprotein B in pedigrees ascertained through a lipid clinic. | journal = American Journal of Human Genetics | volume = 43 | issue = 3| pages = 311–21| year = 1988 | pmid = 3414686 | pmc=1715383}} ==See also== * [Genetic epidemiology](/source/Genetic_epidemiology) * [Genetic segregation](/source/Genetic_segregation) ==References== {{Reflist}} Category:Statistical genetics Category:Epidemiology --- Adapted from the Wikipedia article [Complex segregation analysis](https://en.wikipedia.org/wiki/Complex_segregation_analysis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Complex_segregation_analysis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.