Question

Which type of DNA repair removes the part of the strand having certain types of bulky lesions, like pyrimidine dimers and nucleotides to which various chemical groups have been attached?

a. nucleotide excision repair
b. base excision repair
c. mismatch repair
d. double-strand breakage repair
e. all of the above

Answer 1

Nucleotide excision repair is responsible for removing bulky lesions such as pyrimidine dimers from DNA strands. It operates by cutting out the damaged section and replacing it with correct nucleotides before sealing the strand with DNA ligase.

Step-by-step explanation:

The type of DNA repair that removes the part of the strand having certain types of bulky lesions, like pyrimidine dimers and nucleotides to which various chemical groups have been attached is nucleotide excision repair. This repair mechanism is vital for fixing bulky, helix-distorting lesions such as pyrimidine dimers, which are primarily caused by ultraviolet (UV) light. The process involves several steps: first, an enzyme complex scans the DNA and recognizes the distortion caused by the lesion. Next, the enzyme complex makes cuts on both the 3' and 5' ends of the lesion. The damaged strand is then removed, and the gap is filled with newly synthesized DNA that complements the undamaged strand, with the help of DNA polymerase. Finally, DNA ligase seals the nick, restoring the integrity of the DNA molecule.