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Excision repair

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Excision repair

(Science: molecular biology) mechanism for the repair of environmental damage to one strand of dna (loss of purines due to thermal fluctuations, formation of pyrimidine dimers by uv irradiation).

The site of damage is recognised, excised by an endonuclease, the correct sequence is copied from the complementary strand by a polymerase and the ends of this correct sequence are joined to the rest of the strand by a ligase. The term is sometimes restricted to bacterial systems where the polymerase also acts as endonuclease.