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Punnett square for three-allele case (left) and four-allele case (right). White areas are homozygotes. Colored areas are heterozygotes. Consider an extra allele frequency, r. The two-allele case is the binomial expansion of (p + q) 2, and thus the three-allele case is the trinomial expansion of (p + q + r) 2.
The word "allele" is a short form of "allelomorph" ("other form", a word coined by British geneticists William Bateson and Edith Rebecca Saunders) in the 1900s, [7][8] which was used in the early days of genetics to describe variant forms of a gene detected as different phenotypes. It derives from the Greek prefix ἀλληλο-, allelo ...
Zygosity (the noun, zygote, is from the Greek zygotos "yoked," from zygon "yoke") (/ zaɪˈɡɒsɪti /) is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Most eukaryotes have two matching sets of chromosomes; that is, they are ...
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. [1][2] The first variant is termed dominant and the second is called recessive. This state of having two different variants of the same gene on ...
Evolutionary biology. Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, [1] is the change in the frequency of an existing gene variant (allele) in a population due to random chance. [2] Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. [3]
In cases of incomplete dominance the same segregation of alleles takes place in the F 2-generation, but here also the phenotypes show a ratio of 1 : 2 : 1, as the heterozygous are different in phenotype from the homozygous because the genetic expression of one allele compensates the missing expression of the other allele only partially. This ...
The advantageous extreme allele will increase as a consequence of survival and reproduction differences among the different present phenotypes in the population. The allele fluctuations as a result of directional selection can be independent of the dominance of the allele, and in some cases if the allele is recessive , it can eventually become ...
The "extreme" allele-frequency case (k= 2) had the most homozygosis (least heterozygosis) of any sample. The "middle of the range" case (k= 4) had the least homozygosity (most heterozygosity): they were each equal at 0.50, in fact.