Transition (genetics)

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Definition of transitions and transversions.

In genetics, a transition is a point mutation that changes a purine nucleotide to another purine (AG) or a pyrimidine nucleotide to another pyrimidine (CT). 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.

See also[edit]


  1. ^ Collins DW, Jukes TH (April 1994). "Rates of transition and transversion in coding sequences since the human-rodent divergence". Genomics. 20 (3): 386–96. doi:10.1006/geno.1994.1192. PMID 8034311. 
  2. ^ Mutations & Mutagenesis
  3. ^ Ebersberger I, Metzler D, Schwarz C, Pääbo S (June 2002). "Genomewide comparison of DNA sequences between humans and chimpanzees". Am. J. Hum. Genet. 70 (6): 1490–7. doi:10.1086/340787. PMC 379137Freely accessible. PMID 11992255. 

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