Question

Oxidative damage to DNA can often result in the alteration of a single nucleotide.

Which DNA repair mechanism would repair this type of damage?

Answer 1

Base Excision Repair

Step-by-step explanation:

It is a field of biochemistry and genetics which deals with the repair of damaged DNA all through the cell cycle. Its main function is to remove small, non-helix-distorting base lesions away from the genome.

It prevents mutations from being incorporated into the DNA while it is being copied.

It is initiated by the enzyme DNA glycosylases (it helps pinpoint and exclude destroyed or mismatched nucleobases, allowing for recovering of the basic DNA sequence by follow-on BER enzymes).

Answer 2

Repair mechanism for base cleavage (BER)

Step-by-step explanation:

Repair by base cleavage (BER)

The altered bases are specifically recognized by glycosylases and removed, generating an AP site. The hole is filled by a DNA polymerase that takes the healthy strand as a template. This system arises not only by exposure to external agents, but also by the cell's own activity.

In case of damage in more than one nucleotide, repair by nucleotide excision (NER) is performed.

Nucleotide excision repair (NER)

The damaged area is recognized by UvrA and B, then A and B separate and UvrC enters which forms a complex with endonuclease activity with B. This enzyme cuts the T-dimer and the gap is filled by a DNA polymerase. There is also the TC-NER system (transcription-coupled nucleotide repair system). The alteration of these mechanisms gives rise to diseases such as: Xeroderma pigmentosum, Trichotiodystrophy or Cockayne Syndrome