Neutral mutation
Encyclopedia
In genetics
, a neutral mutation is a mutation
that has no effect on fitness
. In other words, it is neutral with respect to natural selection
.
For example, some mutations in a DNA triplet or codon do not change which amino acid
is introduced: this is known as a synonymous substitution
. Unless the mutation also has a regulatory
effect, synonymous substitutions are usually neutral. Some non-synonymous mutations, i.e. mutations that do change the amino acid, are also neutral: these neutral changes are often to a chemically similar amino acid that works just as well. Such mutations may spread through neutral drift
.
Neutral mutations can accumulate over time due to genetic drift
or genetic draft
. According to the neutral theory of molecular evolution
, while the majority of mutations are deleterious, the majority of mutations that go on to become fixed as differences between species are neutral.
Many or even most mutations to noncoding DNA
are neutral.
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
, a neutral mutation is a mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
that has no effect on fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...
. In other words, it is neutral with respect to natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
.
For example, some mutations in a DNA triplet or codon do not change which amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
is introduced: this is known as a synonymous substitution
Synonymous substitution
A synonymous substitution is the evolutionary substitution of one base for another in an exon of a gene coding for a protein, such that the produced amino acid sequence is not modified. Synonymous substitutions and mutations affecting noncoding DNA are collectively known as silent mutations...
. Unless the mutation also has a regulatory
Regulation of gene expression
Gene modulation redirects here. For information on therapeutic regulation of gene expression, see therapeutic gene modulation.Regulation of gene expression includes the processes that cells and viruses use to regulate the way that the information in genes is turned into gene products...
effect, synonymous substitutions are usually neutral. Some non-synonymous mutations, i.e. mutations that do change the amino acid, are also neutral: these neutral changes are often to a chemically similar amino acid that works just as well. Such mutations may spread through neutral drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
.
Neutral mutations can accumulate over time due to genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
or genetic draft
Genetic hitchhiking
Genetic hitchhiking is the process by which an allele may increase in frequency by virtue of being linked to a gene that is positively selected. Proximity on a chromosome may allow genes to be dragged along with a selective sweep experienced by an advantageous gene nearby...
. According to the neutral theory of molecular evolution
Neutral theory of molecular evolution
The neutral theory of molecular evolution states that the vast majority of evolutionary changes at the molecular level are caused by random drift of selectively neutral mutants . The theory was introduced by Motoo Kimura in the late 1960s and early 1970s...
, while the majority of mutations are deleterious, the majority of mutations that go on to become fixed as differences between species are neutral.
Many or even most mutations to noncoding DNA
Noncoding DNA
In genetics, noncoding DNA describes components of an organism's DNA sequences that do not encode for protein sequences. In many eukaryotes, a large percentage of an organism's total genome size is noncoding DNA, although the amount of noncoding DNA, and the proportion of coding versus noncoding...
are neutral.