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A null allele is a gene variant that lacks the gene's normal function because it either is not expressed, or the expressed protein is inactive. For example, at the gene locus for the ABO blood type carbohydrate antigens in humans, [13] classical genetics recognizes three alleles, I A, I B, and i, which determine compatibility of blood transfusions.
This is an accepted version of this page This is the latest accepted revision, reviewed on 19 September 2024. Science of genes, heredity, and variation in living organisms This article is about the general scientific term. For the scientific journal, see Genetics (journal). For a more accessible and less technical introduction to this topic, see Introduction to genetics. For the Meghan Trainor ...
A gene is a DNA sequence that codes for a diffusible product. This product may be protein (as is the case in the majority of genes) or may be RNA (as is the case of genes that code for tRNA and rRNA). The crucial feature is that the product diffuses away from its site of synthesis to act elsewhere.
The genotype of an organism is its complete set of genetic material. [1] Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. [2] The number of alleles an individual can have in a specific gene depends on the number of copies of each chromosome found in that species, also ...
Allele frequency. Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. [1] Specifically, it is the fraction of all chromosomes in the population that carry that allele over the total population or sample size.
Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. [1] It is distinguished from genetic variability, which describes the tendency of genetic characteristics to ...
where n 11, n 12, n 22 are the observed numbers of the three genotypes, AA, Aa, and aa, respectively, and n 1 is the number of A alleles, where = +. An example Using one of the examples from Emigh (1980), [7] we can consider the case where n = 100, and p = 0.34. The possible observed heterozygotes and their exact significance level is given in ...
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]