Final answer:
During regular DNA synthesis, wrong nucleotides can be removed by the proofreading and nucleotide excision repair mechanisms.
Step-by-step explanation:
The wrong nucleotide placed during regular 5' to 3' DNA synthesis can be removed through proofreading and nucleotide excision repair mechanisms. In proofreading, DNA polymerase reads the newly added base before adding the next one. If an incorrect base has been added, the enzyme cuts the phosphodiester bond and releases the wrong nucleotide. The nucleotide excision repair mechanism removes the incorrect base along with a few bases on the 5' and 3' ends, and these are replaced by copying the template using DNA polymerase.