Transition (genetics)

Transition is a type of genetic mutation that involves a change from a purine base to another purine (A ↔ G) or a pyrimidine base to another pyrimidine (C ↔ T). This is in contrast to a transversion, which is the interchange of a purine for a pyrimidine or a pyrimidine for a purine.

Overview[edit | edit source]

In molecular biology, transition mutations are a form of point mutation that occur due to the replacement of a purine with a purine or a pyrimidine with a pyrimidine. This is a common type of mutation in humans and can lead to various genetic disorders if not repaired by the DNA repair mechanisms in the cell.

File:Transition mutation.png

A transition mutation showing a purine to purine or a pyrimidine to pyrimidine change.

Causes[edit | edit source]

Transition mutations can be caused by a number of factors including oxidative stress, ionizing radiation, and exposure to certain mutagens. They can also occur spontaneously during DNA replication due to the tautomeric shifts in the DNA bases that can change their pairing properties.

Effects[edit | edit source]

The effects of transition mutations can vary greatly depending on the context of the mutation. In some cases, they can be silent, meaning they do not result in any change in the amino acid sequence of the protein. In other cases, they can result in a missense mutation, leading to a change in the amino acid sequence, or a nonsense mutation, leading to a premature stop codon. Both of these can potentially lead to a nonfunctional or malfunctioning protein.