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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.
In Mendelian inheritance, genes have only two alleles, such as a and A. Mendel consciously chose pairs of genetic traits, represented by two alleles for his inheritance experiments. In nature, such genes often exist in several different forms and are therefore said to have multiple alleles. An individual usually has only two copies of each gene ...
Polygenic inheritance can be explained as Mendelian inheritance at many loci, [9] resulting in a trait which is normally-distributed. If n is the number of involved loci, then the coefficients of the binomial expansion of ( a + b ) 2n will give the frequency of distribution of all n allele combinations .
In fact, the terms 'multifactorial' and 'polygenic' are used as synonyms and these terms are commonly used to describe the architecture of disease causing genetic component. [2] Multifactorial diseases are often found gathered in families yet, they do not show any distinct pattern of inheritance.
This model illustrates polygenic additive effects on phenotype Genetic effects are broadly divided into two categories: additive and non-additive. Additive genetic effects occur where expression of more than one gene contributes to phenotype (or where alleles of a heterozygous gene both contribute), and the phenotypic expression of these gene(s ...
It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single genetic cause, either in a gene or chromosome.
Research on ecologically important traits often focuses on single alleles. [17] However, it has been found that in many cases, phenotypes have a polygenic basis - they are controlled by many different alleles. Complex traits in particular are more likely to have a polygenic basis. [18]
To what extent a particular genotype influences a phenotype depends on the relative dominance, penetrance, and expresivity of the alleles in question. One experiences this in everyday life with monozygous (i.e. identical) twins. Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype ...