Final answer:
The statement is TRUE. Nucleotide excision repair is important for repairing DNA damage like thymine dimers, which can happen regardless of transcription accuracy, and involves cutting out damaged DNA, filling it with correct nucleotides, and sealing it. option a.
Step-by-step explanation:
The statement that nucleotide excision repair (NER) needs to function even when DNA has been properly transcribed is TRUE. NER is a critical cellular mechanism that repairs DNA damage affecting longer strands typically of 2-30 bases. This includes bulky, helix-distorting damages such as thymine dimers, which can be caused by UV exposure and lead to mutations if not repaired. A specialized subset of this mechanism is Transcription-Coupled Repair (TCR), which is a high-priority repair system targeting genes that are being actively transcribed.
The process of NER involves enzymes that recognize and remove damaged sections of DNA by making cuts on both the 3' and 5' ends of the damaged base. The erroneous DNA segment is then excised, and the gap is filled with the correct nucleotides by DNA polymerase, followed by sealing the nicks with DNA ligase. It is important to note that NER functions not just to correct errors made during DNA replication, but also to repair damage that occurs to DNA throughout the cell's life, which can be a result of various environmental factors or normal cellular processes.
As such, even when transcription by RNA polymerase takes place without any errors, NER is still essential to maintain the overall integrity of the DNA, ensuring that any damage incurred after the transcription process is promptly and accurately addressed.