Question

In transcription-coupled repair, how is the presence of a lesion thought to be detected?

a. There are special enzymes that scan the DNA for such lesions.
b. The lesion is signaled by a stalled RNA polymerase.
c. The lesion is signaled by a stalled DNA polymerase.
d. The lesion is signaled by a stalled peptidyl transferase.
e. The lesion is detected single-stranded binding proteins

Answer 1

In transcription-coupled repair, the presence of a DNA lesion is detected when RNA polymerase stalls at the site of damage during transcription. This stalling signals repair proteins to the site to remedy the DNA damage, allowing transcription to continue.

Step-by-step explanation:

In transcription-coupled repair (TCR), the presence of a DNA lesion is detected by the stalling of the RNA polymerase during transcription. Upon encountering a damaged site on the DNA, such as a nick or an unusual base substitution, the RNA polymerase ceases its function because it cannot correctly read and transcribe the affected portion of DNA. This stalling of the RNA polymerase signals the need for repair. Proteins then couple with the stalled RNA polymerase, initiating the repair process to fix the DNA lesion and allow transcription to resume correctly. This mechanism is significant as it ensures the integrity of the genetic information during the crucial process of gene expression.

DNA repair is a critical cellular function responsible for maintaining the genetic stability of a cell. Several repair mechanisms exist, including nucleotide excision repair and mismatch repair, to correct various forms of damage like thymine dimers, mismatched bases, and other structural abnormalities in DNA.