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Complex traits are phenotypes that are controlled by two or more genes and do not follow Mendel's Law of Dominance. They may have a range of expression which is typically continuous. Both environmental and genetic factors often impact the variation in expression. Human height is a continuous trait meaning that there is a wide range of heights ...
Under the Polygenic Model, for traits, like height, to be continuous in a population there must be many genes that code for the trait. Otherwise, the expression of the trait is limited by the number of possible combinations of alleles. The many genes which code for the continuous trait are also further modified by environmental conditions. [3]
However, multifactorial traits may be discontinuous or continuous. [citation needed] Continuous traits exhibit normal distribution in population and display a gradient of phenotypes while discontinuous traits fall into discrete categories and are either present or absent in individuals.
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.
They can show either smooth, continuous gradation in a character, or more abrupt changes in the trait from one geographic region to the next. [2] A cline is a spatial gradient in a single specific trait, rather than in a collection of traits; [3] a single population can therefore have as many clines as it has traits, at least in principle. [4]
Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of phenotypic variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color ...
Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene.
A polygene is a member of a group of non-epistatic genes that interact additively to influence a phenotypic trait, thus contributing to multiple-gene inheritance (polygenic inheritance, multigenic inheritance, quantitative inheritance [1]), a type of non-Mendelian inheritance, as opposed to single-gene inheritance, which is the core notion of Mendelian inheritance.