5' to 3' exonuclease activity is seen in:: (A) Proof reading, (B) Repair of damaged DNA, (C) DNA synthesis, (D) DNA polymerase
Answer is B. 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.