Question

Which type of DNA repair is used to remove and replace a single modified base that cannot be converted back to the normal base by a direct repair process?

a) Nucleotide excision repair
b) Base excision repair
c) Mismatch repair
d) Double-strand break repair

Answer 1

Base excision repair is the DNA repair mechanism that removes and replaces a single modified base through a process involving enzymes like DNA glycosylase, DNA polymerase, and DNA ligase.

Step-by-step explanation:

The type of DNA repair used to remove and replace a single modified base that cannot be converted back to the normal base by a direct repair process is base excision repair. This repair mechanism involves a specific enzyme known as a DNA glycosylase, which recognizes and removes the damaged base. Subsequently, an endonuclease cuts the DNA backbone at the site of the base removal, and DNA polymerase fills in the correct nucleotide. Finally, DNA ligase seals the repair with a phosphodiester linkage to complete the process.