Transition (genetics)

For other uses, see Transition.

Illustration of a transition: each of the 4 nucleotide changes between purines or between pyrimidines (in blue). The 8 other changes are transversions (in red).

Transition, in genetics and molecular biology, refers to 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. Although there are twice as many possible transversions, transitions appear more often in genomes,^[2] possibly due to the molecular mechanisms that generate them. ^[3] Transitions are more likely to be synonymous substitutions than transversions, as one observes in the codon table.

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

• Transversion

References

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. 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 379137. PMID 11992255.
3. Mezhzherin, S. V.; Tereshchenko, V. O. (2023-06-01). "Genetic Divergence and Evolutionary Transition/Transversion Rate Bias in the Control Region of Mitochondrial DNA of Palearctic Mice (Murinae)". Cytology and Genetics. 57 (3): 213–220. doi:10.3103/S0095452723030076. ISSN 1934-9440. S2CID 259191096.

External links

• Diagram at mun.ca