Base  excision  repair  in E.
   coli.
<bR>1. A  base  pair  mismatch  is  recognized  by DNA glycosylase, which
removes the base from the sugar, creating an apurinic/apyrimidinic
(AP) site.
<Li> AP  endonuclease makes a cut in the phosphodiester backbone at the
AP site.
<Li> The gap is filled by DNA polymerase I and DNA ligase
<Li> The error is corrected.