Question

Select all of the following that are true about nucleotide excision repair (NER):

1) The undamaged strand is used as a template to synthesize a normal strand
2) A region of several nucleotides in the damaged strand is removed from the sequence
3) Both DNA strands are removed and an enzyme complex resynthesizes new DNA
4) Only the altered DNA nucleotide is removed and replaced with normal DNA

Answer 1

In nucleotide excision repair (NER), the undamaged DNA strand is used as a template to correct the damaged strand. A section of the damaged strand including the error is removed and replaced with the correct sequence via the actions of DNA polymerase and DNA ligase. The accurate statements about NER are therefore 1) and 2).

Step-by-step explanation:

Nucleotide excision repair (NER) is a vital cellular process that corrects DNA damage, particularly bulky lesions such as thymine dimers resulting from UV exposure. Here are the truths about NER:

• The undamaged strand is used as a template to synthesize a normal strand, ensuring that the repaired DNA matches the original sequence.
• A region of several nucleotides in the damaged strand is removed. This includes the erroneous bases and some of the surrounding nucleotides on both the 5' and 3' ends of the damage site.
• Only the damaged DNA segment is removed, not both DNA strands. An enzyme complex, including DNA polymerase and DNA ligase, then fills in the gap and seals it with a phosphodiester bond.

Thus, the correct statements about NER would be 1) and 2). NER is highly specific and effective in repairing damaged DNA while preserving genetic integrity.