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Human height is a continuous trait meaning that there is a wide range of heights. There are an estimated 50 genes that affect the height of a human. Environmental factors, like nutrition, also play a role in a human's height. Other examples of complex traits include: crop yield, plant color, and many diseases including diabetes and Parkinson's ...
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.
A study of recent polygenic adaptation in the English has shown that selection on height has had small effects on allele frequencies (<1%) across most of the genome, and found evidence for polygenic adaptation in a wide variety of other traits as well including selection for increased infant birth size and increased female hip and waist size. [10]
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.
With these traits as being by-products of others it can ultimately be said that these traits evolved but not that they necessarily represent adaptations. Polygenic traits are controlled by a number of separate genes. Many traits are polygenic, for example human height. To drastically change a polygenic trait is likely to require multiple changes.
X-linked recessive inheritance. X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity.
We are able to treat biological traits as manifestations of either a single loci or multiple loci, labeling said biological traits as either monogenic or polygenic, respectively. [12] Concerning polygenic traits it may be essential to be mindful of inter-genetic interactions or epistasis. Although epistasis is a significant genetic source of ...
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]