Final answer:
The errors that cause bulky distortions in the DNA double helix are repaired by a system called Nucleotide Excision Repair (NER), especially those caused by thymine dimers, and this process is essential for maintaining genomic stability and preventing mutations.option a is correct answer.
Step-by-step explanation:
Some errors in the DNA create bulky distortions of the double helix and are primarily removed by a DNA repair system called Nucleotide Excision Repair (NER). This essential repair mechanism specifically repairs damage that affects longer strands of 2-30 bases, including those caused by thymine dimers and single-strand breaks.
Thymine dimers, often induced by UV radiation, are a type of damage in which two thymine nucleotides adjacent to each other on one strand form a covalent bond. The NER process is complex, encompassing the unwinding of the DNA double helix, recognition and removal of the damaged segment, and gap filling by DNA polymerase followed by ligation to restore the DNA's integrity.
Moreover, the related process of Transcription-Coupled Repair (TCR) is a specialized form of NER that focuses on genes being actively transcribed, ensuring that the transcription machinery can continue to function properly without interruption caused by DNA damage. In individuals with defective NER mechanisms, such as those with the condition xeroderma pigmentosum, there's a marked increase in sensitivity to sunlight and a significantly higher risk of developing skin cancers early in life. This underscores the critical role that NER plays in maintaining the genomic stability.