Britannica Sources used in this answer

How do DNA transitions differ from DNA transversions?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A diagram showing the tentative evolutionary relationships among hominid species over the past four million years, with skull images and labeled species names connected by solid and dotted lines to indicate proposed evolutionary pathways. — phylogeny Tentative phylogenetic scheme for the evolution of the human lineage. Solid bars indicate the time ranges during which species are thought to have existed, based on fossil evidence. Dotted lines signify evolutionary relationships between hominin species that have been proposed on the basis of the fossil evidence.

In the study of phylogeny and molecular evolution, DNA transitions and transversions are two distinct types of point mutations that describe how a single base pair is altered within a sequence.

Transitions: These occur when a pyrimidine base (thymine or cytosine) is substituted for another pyrimidine, or when a purine base (adenine or guanine) is substituted for another purine.12
Transversions: These occur when a purine base is substituted for a pyrimidine base, or vice versa.12

In evolutionary biology, these distinctions are significant because they are not equally probable. Transitions are generally more likely to occur than transversions. Consequently, when researchers use maximum parsimony methods to reconstruct evolutionary trees, they often account for these different probabilities to more accurately model the history of genetic change.2