DNA ligase then forms a phosphodiester bond to seal the resulting nicked duplex product, which now includes a new, correct cytosine (Base excision repair).
In DNA, this reaction, if detected prior to passage of the replication fork, can be corrected by the enzyme thymine-DNA glycosylase, which removes the thymine base in a G/T mismatch.
Cytosine deamination can alter the genome's many regulatory functions; previously silenced transposable elements (TEs) may become transcriptionally active due to the loss of CPG sites.
[3] TEs have been proposed to accelerate the mechanism of enhancer creation by providing extra DNA that is compatible with the host transcription factors that eventually have an impact on C-to-T mutations.
Hypoxanthine, in a manner analogous to the imine tautomer of adenine, selectively base pairs with cytosine instead of thymine.