Final answer:
Base excision repair is the DNA repair mechanism that removes nucleotides altered by reactive chemicals, which is proficient in fixing DNA with minimal helix distortion.
Step-by-step explanation:
The DNA repair mechanism that removes nucleotides altered by reactive chemicals present in the diet or produced by metabolism is base excision repair. This mechanism is efficient in repairing DNA where the helix is less distorted. Specialized enzymes called DNA glycosylases initiate base excision repair by recognizing and removing the damaged base. The resulting abasic site is further processed by additional enzymes that cut the DNA backbone, remove a short stretch of nucleotides including the abasic site, and fill in the correct bases.
This is different from nucleotide excision repair, which deals with bulky lesions such as thymine dimers that significantly distort the DNA helix. Nucleotide excision repair enzymes make cuts on both 3' and 5' ends of the damage and remove a longer sequence of nucleotides.