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:This article is about mutation in biology, for other meanings see: mutation (disambiguation).Mutations are permanent, transmissible changes to the genetic material (usually DNA or RNA) of a cell. Mutations can be caused by copying errors in the genetic material during cell division and by exposure to radiation, chemicals, or viruses, or can occur deliberately under cellular control during the processes such as meiosis or hypermutation . In multicellular organisms, mutations can be subdivided into germline mutations, which can be passed on to progeny and somatic mutations, which (when accidental) often lead to the malfunction or death of a cell and can cause cancer. Mutations are considered the driving force of evolution, where less favorable (or deleterious) mutations are removed from the gene pool by natural selection, while more favorable (or beneficial) ones tend to accumulate. Neutral mutations do not affect the organism's chances of survival in its natural environment and can accumulate over time, which might result in what is known as punctuated equilibrium; the modern interpretation of classic evolutionary theory.
It should be noted that, contrary to science fictionScience fiction generally speaking, is a form of speculative fiction which deals principally with the impact of imagined science and/or technology upon society or individuals. There are, perhaps, exceptions to (or at least, some very unusual examples of), the overwhelming majority of mutations have no real effect.
Mutagenesis is the process by which mutations arise. Both words originate from the Latin mutare, to change.
1 Types of mutations
Basic types of mutations are:
- Point mutationA point mutation is a type of mutation that causes the replacement of a single base pair with another pair. There are several types of point mutations, including nonsense mutations, missense mutations, and silent mutations. For example, sickle-cell anemias are usually caused by chemicals or malfunction of DNA replication and exchange a single nucleotideA nucleotide is an organic molecule consisting of a nitrogenous heterocyclic base (a purine or a pyrimidine), a pentose sugar ( deoxyribose in DNA or ribose in RNA), and a phosphate or polyphosphate group. A nucleoside is similar, except that it contains for another. Most common is the transition that exchanges a purineA purine is a bicyclic organic compound, consisting of a fused pyrimidine/ imidazole ring. Two of the bases in nucleic acids, adenine and guanine, are purines. In DNA, these bases form hydrogen bonds with their complementary pyrimidines thymine and cytosi for a purine or a pyrimidinePyrimidine is an organic compound, a conjugated amine which is similar to benzene, but with a heterocyclic ring: two nitrogen atoms taking the place of carbon atoms at positions 1 and 3 relative to each other around the six-member ring. Three bases of the for a pyrimidine (A ↔ G, C ↔ T). A transition can be caused by nitrous acidNitrous acid weak monobasic acid known only in solution and in the form of nitrite salts. Formula: HNO Systematic name: dioxonitric(III) acid Nitrous acid is used to make diazides from amines; this occurs by nucleophilic attack of the amine onto the nitri, base mispairing, or mutagenic base analogs such as 5-bromo-2-deoxyuridine (BrdU)Also known as 5-bromo-2-deoxyuridine, this chemical is a base analog of thymidine, with the thymine substituted by bromouracil. Because BrdU can replace thymidine, excessive exposure to the chemical can cause mutations. BrdU is a common chemical used in t. Less common is a transversion, which exchanges a purine for a pyrimidine or a pyrimidine for a purine (C/T ↔ A/G). A point mutation can be reversed by another point mutation, in which the nucleotide is changed back to its original state (true reversion) or by second-site reversion (a complementary mutation elsewhere that results in regained gene functionality). Point mutations are called silent, missense or nonsense mutations, depending on whether the erroneous codon codes for the same amino acidIn chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. In biochemistry, this shorter and more general term is frequently used to refer to alpha amino acids: those amino acids in which the amino and carb (silent), a different amino acid (missense) or a stop, which can truncate the protein (nonsense).
- Insertions add one or more extra nucleotides into the DNA. They are usually caused by transposable elements, or errors during replication of repeating elements (e.g. AT repeats). Most insertions in a gene can cause a shift in the reading frame ( frameshift) or alter splicing of the mRNA, both of which can significantly alter the gene product. Insertions can be reverted by excision of the transposable element.
- Deletions remove one or more nucleotides from the DNA. Like insertions, these mutations can alter the reading frame of the gene. They are irreversible.
