Which repair process targets bulky DNA lesions that distort the helix?

Which repair process targets bulky DNA lesions that distort the helix?

• A. Base excision repair targets bulky lesions.
• B. Double-strand break repair targets bulky lesions.
• C. Nucleotide excision repair targets bulky DNA lesions that distort the helix.
• D. Mismatch repair targets bulky lesions.

Answer: (C)

The concept being tested is which repair pathway handles bulky, helix-distorting DNA damage. Bulky lesions like UV-induced pyrimidine dimers distort the DNA helix, and nucleotide excision repair is specialized to recognize and remove these distortions. The process involves detecting the lesion, locally unwinding the DNA, making incisions on either side of the damaged segment, and excising a short DNA fragment that contains the damage. The gap is then filled in by DNA polymerase and sealed by DNA ligase. This targeted removal of a short stretch surrounding the distortion is what sets nucleotide excision repair apart from other pathways. Base excision repair handles small, non-helix-distorting base modifications or abasic sites, not bulky distortions. Double-strand break repair deals with breaks in both DNA strands rather than bulky chemical lesions. Mismatch repair fixes replication mistakes like mispaired bases, not large distortions in the helix.

The concept being tested is which repair pathway handles bulky, helix-distorting DNA damage. Bulky lesions like UV-induced pyrimidine dimers distort the DNA helix, and nucleotide excision repair is specialized to recognize and remove these distortions. The process involves detecting the lesion, locally unwinding the DNA, making incisions on either side of the damaged segment, and excising a short DNA fragment that contains the damage. The gap is then filled in by DNA polymerase and sealed by DNA ligase. This targeted removal of a short stretch surrounding the distortion is what sets nucleotide excision repair apart from other pathways.

Base excision repair handles small, non-helix-distorting base modifications or abasic sites, not bulky distortions. Double-strand break repair deals with breaks in both DNA strands rather than bulky chemical lesions. Mismatch repair fixes replication mistakes like mispaired bases, not large distortions in the helix.