7. Correcting DNA replication errors Aa Aa The accuracy of DNA replication is ma

Question

7. Correcting DNA replication errors Aa Aa The accuracy of DNA replication is maintained by both proofreading and DNA repair. Complete the following table to compare these two error correction mechanisms Proofreading DNA Repair Specialized enzymes first remove the incorrect nucleotide, and then DNA polymerase adds the correct one. Only the mismatched nucleotide is removed When correcting a mismatch, repair enzymes must be able to tell which strand was the (originally correct) template strand. Certain bacteria such as Escherichia coli solve this problem by using an enzyme called Dam methylase. This enzyme scans Methyl groups O Type here to search 0 DOLL F6 F7

Explanation / Answer

Specialized enzyme first removes the incorrect nucleotide and then DNA Polymerase adds the correct one: DNA repair Only the mismatched nucleotide is removed: Proofreading These are the specialties of key enzymes of DNA replication. DNA Polymerases have proofreading activities. Upon recognition of an incorrect base, the direction of DNA Polymerase is reversed and correct base is incorporated. Enzyme like Dam methylase is involved in DNA repair in prokaryotes like E. coli. The newly formed DNA strand is hemimethylated and endonuclease MutH is activated. The incorrect strand is excised by recruiting helicase and exonuclease and then Polymerase enzyme synthesizes the correct strand. This is the mechanism of DNA Repair.

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