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Allele in Biological Definition

Allele

... An allele is any one of a number of alternative forms of ... the gene are identical - that is, have the same allele - is said to be homozygous for that gene. An ... the gene is said to be heterozygous . Often one allele is "dominant" and the other is "recessive" - the ...

Allele frequency

... allele frequency is a term of population genetics ... or equivalently the richness of its gene pool . allele frequency is defined as follows: Given a) a ... sets of chromosomes) and finally d) a variant or allele of the gene, then the ...

Evolution

... means a change in the frequency of an allele within a gene pool . This change may be caused ... drift Genetic drift describes changes in allele frequency that cannot be ascribed to selective ... to generation can be large. Such fluctuations in allele frequency between successive generations may ...

Gene

... more precisely, a biologist might refer to an allele or a mutation that has been implicated in or ... for example eye color. A gene's most common allele is called the wild type allele, and rare ... dominance relationships (more at genetics , allele ). Expression of molecular genes For ...

Genetic drift

... Contents showTocToggle("show","hide") 1 allele frequencies 2 Drift versus selection 3 ... 4 See also 5 External link allele frequencies From the perspective of population ... Similarly, in a breeding population, if an allele has a frequency of p , probability theory ...

Genetics

... defined a concept that he described as an allele , which was the fundamental unit of heredity. The term allele as Mendel used it is nearly synonymous with the term gene , whilst the term allele now means a specific variant of a particular ...

Hardy-Weinberg principle

... can be represented as a simple function of the allele frequencies at that locus. In the simplest ... a single locus with two alleles A and a with allele frequencies of p and q , respectively, the HWP ... together males and females with different allele frequencies, in which case, equilibrium is ...

Major histocompatibility complex

... are quite ancient: it is often the case that an allele from a particular HLA gene is more closely related to an allele found in chimpanzees than it is to another human allele from the same gene! The allelic diversity of ...

Molecular evolution

... 2.1 Mutations 2.2 Causes of change in allele frequency 2.3 Molecular study of phylogeny ... evolutionary theory. Causes of change in allele frequency Main article: Population genetics ... or, more specifically, the frequency of an allele (variant of a gene ): Mutation detailed ...

Neutral theory of molecular evolution

... genetic drift acting on neutral alleles . A new allele arises typically through the spontaneous ... such an event immediately contributes a new allele to the population, and this allele is subject to drift. In sexually reproducing , ...

Blood type

... long arm of the ninth chromosome (9q34). A allele gives type A, B gives type B, and i gives ... Evolutionary biologists theorize that the A allele evolved earliest, followed by O and then B . ... to the A and B antigens. For instance, the B allele must be present to produce the B enzyme that ...

Genetic recombination

... , a cell carries two copies of each gene , each referred to as an allele . Each parent passes on one allele to each offspring. Even without recombination, each gamete contains a ...

Mendelian inheritance

... This means that when somatic cells are produced from two gametes, one allele comes from the mother, one from the father. These alleles may be the same ... (2) F 1 generation. (3) F 2 generation. The " red " and "white" allele together make a " pink " phenotype, resulting in a 1:2:1 ratio of red : ...

Barr body

... inactivated. This can be significant if different alleles of a gene are present on the different chromosomes; in some regions of the body one allele will be active, and in other regions the other will. This is what results in the coloration pattern of female calico cats ; pigmentation genes on ...

Ewens's sampling formula

... statistical equilibrium under mutation and genetic drift and the role of selection at the locus in question is negligible, and (3) every mutant allele is novel. This is a probability distribution on the set of all partitions of the integer n . Among probabilists and statisticians it is often ...

Gene therapy

... cells and tissues to treat a disease , and hereditary diseases in particular. Gene therapy typically aims to supplement a defective mutant allele with a functional one. Although the technology is still in its infancy, it has been used with some success. Antisense therapy is not strictly a ...

Heterozygote

... protein product coded for by the gene in question. In some cases a mixture of normal and abnormal proteins is produced. In other cases, the abnormal allele may produce no protein at all. If the proteins are enzymes, the less-functional enzyme molecules usually have no effect and the person is an ...

Isozyme

... of the gene . As with any other new mutation , there are three things that may happen to a new allozyme: (1) It is most likely that the new allele will be non-functional - in which case it will probably result in low fitness and be removed from the population by natural selection . ...

Locus

... . A locus can be occupied by any of the alleles of the gene. Diploid or polyploid cells are either homozygous (have the same allele at a locus) or heterozygous (have different alleles at a locus). In mathematics , a locus is the set of points satisfying a particular ...

Meiosis

... heritable variation. The reduction of chromosomes from the diploid to the haploid condition separates alleles so that each gamete carries a sole allele for a gene locus. In addition, the orientation of the metaphase I/II equatorial lining-up is random, resulting in new allelic recombinationis. ...

Polymerase chain reaction

... identification of a Russian tsar . Genotyping of specific mutations Through the use of allele-specific PCR, one can easily determine which allele of a mutation or polymorphism an individual has. Here, one of the two primers is common, and would anneal a short distance away from the mutation, ...

Population genetics

... Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection , genetic drift , mutation and migration . It also takes ...

Reverse genetics

... approach, geneticists first look for rare individuals with unusual traits or phenotypes , and then they trace these traits to an underlying faulty allele or gene. Locating the gene on its chromosome is the end point of an investigation. With the readily performed modern techniques of DNA ...

Thomas Hunt Morgan

... suggesting that the white eye trait was recessive. Morgan thus named the gene white , starting the tradition of naming genes after their mutant allele . As Morgan continued to cross-breed the mutants back to one another, he noticed that only males displayed the white-eyed trait. From this, he ...

Trait

... flow charted above. For example, if the alleles on homologous chromosomes exhibit a "simple dominance " relationship, the trait of the "dominant" allele shows in the phenotype . Gregor Mendel pioneered modern genetics. His most famous analyses were based on clear-cut traits with simple dominance. ...
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