Nucleotide excision repair.
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   A  thymine  dimer, a type of damage often caused by excessive exposure
   to ultraviolet radiation.
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   A nuclease enzyme cuts out (excises) the damaged nucleotides.
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   DNA polymerase replaces it with a normal DNA segment.
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   DNA   ligase   completes  the  process  by  closing  the  gap  in  the
   sugar-phosphate backbone.