This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': "5' to 3' exonuclease activity is seen in: \nSelect and explain. \nA. Proof reading, B. Repair of damaged DNA, C. DNA synthesis, D. DNA polymerase", 'role': 'user'}, {'content': "Answer: B \nExplanation: 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.", 'role': 'assistant'}]