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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.
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]
Offspring of the males with the trait don't inherit the trait. Offspring of the females with the trait always inherit the trait (independently from their own sex). Extranuclear inheritance (also known as cytoplasmic inheritance) is a form of non-Mendelian inheritance also first discovered by Carl Correns in 1908. [9]
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 ...
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).
Autosomal traits are associated with a single gene on an autosome (non-sex chromosome)—they are called "dominant" because a single copy—inherited from either parent—is enough to cause this trait to appear. This often means that one of the parents must also have the same trait, unless it has arisen due to an unlikely new mutation.
Maternal influences may also be possible that affect sex determination in such a way as to produce fraternal twins equally weighted between one male and one female. [ 28 ] The time at which insemination occurs during the estrus cycle has been found to affect the sex ratio of the offspring of humans, cattle, hamsters, and other mammals. [ 25 ]
In the ZW sex-determination system used by birds, the mammalian pattern is reversed, since the male is the homogametic sex (ZZ) and the female is heterogametic (ZW). In classical genetics, a mating experiment called a reciprocal cross is performed to test if an animal's trait is sex-linked.