Biology / Unit 6 Bio 1239 short lesson, about 20 seconds
DNA Polymerase Proofreading
Captions available
The idea
DNA polymerase proofreads each newly added nucleotide, using an exonuclease activity to remove and replace a mismatched base before continuing synthesis.
In practice
DNA polymerase pauses when a newly added base fails to pair correctly, then reverses to excise that base and try again.
Where people slip
Proofreading corrects errors during synthesis itself — a distinct step from the repair mechanisms that act on DNA afterward.
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