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Fixation (population genetics)

 

 
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Fixation (population genetics)
 
 
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In population genetics
Population genetics

Population genetics is the study of the allele frequency distribution and change under the influence of the four evolutionary processes: natural selection, genetic drift, mutation and gene flow....
, fixation is the change in a gene pool
Gene pool

In population genetics, a gene pool is the complete set of unique alleles in a species or population....
 from a situation where there exists at least two variants of a particular gene (allele
Allele

An allele is one member of a pair or series of different forms of a gene. Usually alleles are coding region, but sometimes the term is used to refer to a junk DNA....
) to a situation where only one of the alleles remains. The term can refer to a gene in general or particular nucleotide
Nucleotide

Nucleotides are molecules that comprise the structural units of RNA and DNA. Additionally, nucleotides play central roles in metabolism. In that capacity, they serve as sources of chemical energy , participate in cell signaling , and are incorporated into important cofactors of enzymatic reactions ....
 position in the DNA chain (locus
Locus (genetics)

In the fields of genetics and evolutionary computation, a locus is a fixed position on a chromosome such as the position of a genetic marker that may be occupied by one or more genes....
).

In the process of substitution a previously non-existant allele arises by mutation
Mutation

In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or virus , or can be induced by the organism, itself, by cellular processes such as s...
 and undergoes fixation by spreading through the population by random genetic drift
Genetic drift

Genetic drift or allelic drift is the change in the relative frequency with which a gene variant occurs in a population that results from the fact that alleles in offspring are a Sampling of those in the parents, and because of the role of chance in determining whether a given individual survives and reproduces....
 and/or positive selection
Natural selection

Natural selection is the process by which favorable heritable trait become more common in successive generations of a population of Reproduction organisms, and unfavorable heritable traits become less common, due to differential reproduction of genotypes....
.






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In population genetics
Population genetics

Population genetics is the study of the allele frequency distribution and change under the influence of the four evolutionary processes: natural selection, genetic drift, mutation and gene flow....
, fixation is the change in a gene pool
Gene pool

In population genetics, a gene pool is the complete set of unique alleles in a species or population....
 from a situation where there exists at least two variants of a particular gene (allele
Allele

An allele is one member of a pair or series of different forms of a gene. Usually alleles are coding region, but sometimes the term is used to refer to a junk DNA....
) to a situation where only one of the alleles remains. The term can refer to a gene in general or particular nucleotide
Nucleotide

Nucleotides are molecules that comprise the structural units of RNA and DNA. Additionally, nucleotides play central roles in metabolism. In that capacity, they serve as sources of chemical energy , participate in cell signaling , and are incorporated into important cofactors of enzymatic reactions ....
 position in the DNA chain (locus
Locus (genetics)

In the fields of genetics and evolutionary computation, a locus is a fixed position on a chromosome such as the position of a genetic marker that may be occupied by one or more genes....
).

In the process of substitution a previously non-existant allele arises by mutation
Mutation

In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or virus , or can be induced by the organism, itself, by cellular processes such as s...
 and undergoes fixation by spreading through the population by random genetic drift
Genetic drift

Genetic drift or allelic drift is the change in the relative frequency with which a gene variant occurs in a population that results from the fact that alleles in offspring are a Sampling of those in the parents, and because of the role of chance in determining whether a given individual survives and reproduces....
 and/or positive selection
Natural selection

Natural selection is the process by which favorable heritable trait become more common in successive generations of a population of Reproduction organisms, and unfavorable heritable traits become less common, due to differential reproduction of genotypes....
. Once the frequency
Allele frequency

Allele frequency is the number of copies of a particular allele divided by the number of copies of all alleles at the genetic place in a population....
 of the allele is at 100%, i.e. being the only gene variant present in any member, it is said to be "fixed" in the population.

Similarly, genetic differences between taxa are said to have been fixed in each species
Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring....
.