QuestionSBA
QuestionChoice
This repair method can only be used to fix single-strand defects. It involves recognising DNA damage, incising on either side to remove the damaged fragment, adding new nucleotides by DNA polymerase, and then sealing the lesion with DNA ligase.
10007002
b
Base excision repair
QuestionChoice
This repair method can be used to fix double-stranded defects but works differently to non-homologous end joining as there is a copying process involving homologous recombination from the second chromosome, restoring the original complete sequence. It does therefore not create defective DNA.
10007005
e
Homologous recombination
QuestionChoice
This repair method can only be used to fix single-strand defects. It works similarly to base excision repair but is used for bulkier and larger lesions of multiple bases, removing the affected nucleotides with DNA helicase and then repairing with DNA polymerase and ligase.
10007003
c
Nucleotide excision repair
QuestionChoice
This mechanism ligates two broken ends together, resulting in a region of DNA with altered segments due to missing nucleotides. This loss of nucleotides occurs due to degradation from both ends. It is used for fixing double-strand breaks specifically, not single-strand defects, and the loss of nucleotides can cause different proteins to be transcribed as a result.
10007001
a
Non-homologous end joining
QuestionChoice
This repair method can only be used to fix single strand defects. When there is an error in a newly made strand, mismatch proofreading proteins bind. DNA repair protein MutS binds to the mismatched base pair and DNA repair protein MutL scans nearby DNA and triggers strand removal to the mismatch.
10007004
d
Mismatch repair
Concept
Chapter
2693
3888
DNA
Topic
181
Structure and Function of Cells
13947
DNA repair involves a collection of mechanisms by which the cell maintains the integrity of its genetic code.

Which of the following is a repair mechanism for double strand breaks that creates defective DNA?
a