Transition (genetics)

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For other uses, see Transition.

Definition of transitions and transversions.

In genetics, a transition is a point mutation that changes a purine nucleotide to another purine (A ↔ G) or a pyrimidine nucleotide to another pyrimidine (C ↔ T). Approximately two out of three single nucleotide polymorphisms (SNPs) are transitions.^[1]

Transitions can be caused by oxidative deamination and tautomerization.^[2] Although there are twice as many possible transversions, transitions appear more often in genomes, possibly due to the molecular mechanisms that generate them.^[3]

5-Methylcytosine is more prone to transition than unmethylated cytosine, due to spontaneous deamination. This mechanism is important because it dictates the rarity of CpG islands.

References[edit]

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Mechanisms of mutation

Mutation with respect to structure

Point mutation	Nonsense mutation Missense mutation Conservative mutation Silent mutation Frameshift mutation Dynamic mutation

Large-scale mutation	Chromosomal translocations Chromosomal inversions

Mutation with respect to overall fitness

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