<prompt> 5 to 3 exonuclease activity is seen in:Proof readingRepair of damaged DNADNA synthesisDNA polymerase  <response>: Ans. b Repair of damaged DNARef: Harpers Biochemistry, 30th ed. pg. 389-90Two types of exonuclease activity has been described: 5 to 3 exonuclease activity: responsible for cleavage of phosphodiester bond starting from 5 end of the strand. It is considered as the error correcting activity in damaged DNA. 3 to 5 exonuclease activity: responsible for cleavage of phosphodiester bond starting from 3 end of the strand. This activity provides a means for proofreading if in case any wrong base is mistakenly incorporated by DNA polymerase III during DNA synthesis. 