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It is a complex trait because multiple genetic and environmental factors impact the phenotype. [13] [14] The phenotype before the threshold is referred to as normal or absent, and after the threshold as lethal or present. These traits are often examined in a medical context, because many diseases exhibit this pattern or similar. [9]
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.
Genotype contributes to phenotype, the observable traits and characteristics in an individual or organism. [3] The degree to which genotype affects phenotype depends on the trait. For example, the petal color in a pea plant is exclusively determined by genotype. The petals can be purple or white depending on the alleles present in the pea plant ...
[1] [2] Intelligence in the normal range is a polygenic trait, meaning that it is influenced by more than one gene, [3] [4] and in the case of intelligence at least 500 genes. [5] Further, explaining the similarity in IQ of closely related persons requires careful study because environmental factors may be correlated with genetic factors.
Traits controlled by two or more genes are said to be polygenic traits. Polygenic means "many genes" are necessary for the organism to develop the trait. For example, at least three genes are involved in making the reddish-brown pigment in the eyes of fruit flies. Polygenic traits often show a wide range of phenotypes.
For example, Mendel focused on traits whose genes have only two alleles, such as "A" and "a". However, many genes have more than two alleles. He also focused on traits determined by a single gene. But some traits, such as height, depend on many genes rather than just one. Traits dependent on multiple genes are called polygenic traits.
The infinitesimal model, also known as the polygenic model, is a widely used statistical model in quantitative genetics and in genome-wide association studies.Originally developed in 1918 by Ronald Fisher, it is based on the idea that variation in a quantitative trait is influenced by an infinitely large number of genes, each of which makes an infinitely small (infinitesimal) contribution to ...
Phenotypes (measurable traits), such as height or risk for heart disease, are the product of some combination of genes and environment. These traits can be estimated using polygenic scores, which seek to isolate and estimate the contribution of genetics to a trait by summing the effects of many individual genetic variants. To construct a score ...