Question

Give the detailed description of the base excision (or nucleotide excision) repair process in bacteria.

A) Base excision repair involves the removal of damaged bases, followed by gap filling.
B) Nucleotide excision repair corrects errors in base pairing during replication.
C) Base excision repair specifically targets pyrimidine dimers caused by UV radiation.
D) Nucleotide excision repair only occurs in eukaryotes, not bacteria.

Answer 1

Nucleotide excision repair in bacteria fixes damaged DNA, such as thymine dimers from UV light, through a process involving detection, excision, and replacement of the damaged segment followed by a ligation.

Step-by-step explanation:

The detailed description of the nucleotide excision repair process in bacteria involves the repair of DNA segments containing damaged bases such as thymine dimers, commonly caused by UV radiation. This DNA repair mechanism involves several steps:

• Recognition of distortion in the DNA helix caused by damage such as thymine dimers by an enzyme complex.
• Excision of the damaged strand by making cuts several bases upstream and downstream of the damage using enzymes like the UvrABC endonuclease complex.
• Removal of the damaged segment of DNA.
• Replacement of the missing nucleotides with the correct ones by DNA polymerase I.
• Sealing of the gap in the sugar-phosphate backbone by DNA ligase to complete the repair.

This repair system is highly conserved in evolution due to its vital role in maintaining genomic integrity and is present in both bacteria and eukaryotes, contrary to the claim of option D that it only occurs in eukaryotes.