Practice question

Nick translation is coupled exonuclease and polymerase reaction moving nick position along duplex without net synthesis. Pol I binds nick bearing free 3' OH, degrades downstream strand via 5' to 3' exonuclease while extending 3' end with polymerase activity incorporating new dNTPs, effectively translating nick along DNA. Property historically exploited to label DNA probes with radioactive dNTPs replacing strand segment uniformly. Pol III cannot degrade downstream duplex, ligase only seals nicks without synthesis. In vivo role of Pol I during Okazaki fragment processing directly mirrors laboratory nick translation mechanism.