Point mutation

Point mutation
Illustration of three types of point mutations.

A point mutation, or single base substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA. Often the term point mutation also includes insertions or deletions of a single base pair. One can categorize point mutations as follows:

  • transitions: replacement of a purine base with another purine or replacement of a pyrimidine with another pyrimidine
  • transversions: replacement of a purine with a pyrimidine or vice versa.

Transition mutations are about an order of magnitude more common than transversions. Point mutations can also be categorized functionally:

  • conservative mutations: result in an amino acid change; however, the properties of the amino acid remain the same (e.g. hydrophobic, hydrophilic, etc).
  • non conservative mutations: result in an amino acid change that has different properties than the wild type.

For example, sickle-cell disease is caused by a single point mutation (a missense mutation) in the beta-hemoglobin gene that converts a GAG codon into GUG, which encodes the amino acid valine rather than glutamic acid. This is an example of a non-conservative (missense) mutation.

Point mutations that occur in non-coding sequences are most often without consequences, although there are exceptions. If the mutated base pair is in the promoter sequence of a gene, then the expression of the gene may change. Also, if the mutation occurs in the splicing site of an intron, then this may interfere with correct splicing of the transcribed pre-mRNA.

Sometimes the term point mutation is also used to describe insertions or deletions of a single base pair (which has more of an adverse effect on the synthesized protein due to the nucleotides' still being read in triplets, but in different frames: a mutation called a frameshift mutation).

A "point mutant" is an individual which is affected by a point mutation.


Point mutations may arise from spontaneous mutations that occur during DNA replication. The rate of mutation may be increased by mutagens. Mutagens can be physical, such as radiation from UV rays, X-rays or extreme heat, or chemical (molecules that misplace base pairs or disrupt the helical shape of DNA). Mutagens associated with cancers are often studied to learn about cancer and its prevention.

Transitions (Alpha) and transversions (Beta).

There is a systematic difference in rates for transitions (Alpha) and transversions (Beta).

External links

Mutation with respect to overall fitness.
Deleterious mutation  · Advantageous mutation  · Neutral mutation  · Nearly neutral mutation

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Look at other dictionaries:

  • point mutation — point mutation. См. точковая мутация. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Point mutation — A single nucleotide base change in the DNA. A point mutation may consist of the loss of a nucleotide, the insertion of an additional nucleotide, or the substitution of one nucleotide for another. The first point mutation discovered in humans… …   Medical dictionary

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  • point mutation — noun (genetics) a mutation due to an intramolecular reorganization of a gene • Syn: ↑gene mutation • Topics: ↑genetics, ↑genetic science • Hypernyms: ↑mutation, ↑genetic mut …   Useful english dictionary

  • point mutation — noun Date: 1925 a gene mutation involving the substitution, addition, or deletion of a single nucleotide base …   New Collegiate Dictionary

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  • point mutation — noun A mutation that involves the replacement, addition or deletion of a small number of bases (especially just one) at a specific site within a gene …   Wiktionary

  • point mutation — noun Genetics a mutation affecting only one nucleotide in a gene sequence …   English new terms dictionary

  • point mutation — Mutationthat causes the replacement of a single base pair with another pair …   Dictionary of molecular biology

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