Final answer:
Excision and repair on the newly synthesized strand involve removing the incorrect bases and a few adjacent nucleotides, then using the complementary strand as a template to repair the DNA with the help of DNA polymerase and sealing the final gap with DNA ligase.
Step-by-step explanation:
When excision and repair are done on only the newly synthesized strand, it involves a process where the DNA double helix is specifically recognized for damage on the new strand, unwound, and separated at the site of a nucleotide error. The incorrect bases are removed, including a few nucleotides on both the 5' and 3' ends of the error. Once the damaged section is excised, nucleotide excision repair (NER) uses the undamaged, complementary strand as a template to fill in the correct nucleotides by the action of DNA polymerase. Then, DNA ligase seals the remaining gap with a phosphodiester bond, effectively restoring the DNA to its correct sequence and structure.
This repair mechanism is crucial for maintaining the integrity of the DNA and for preventing mutations that may result from unrepaired errors. It is particularly significant in the correction of damage such as thymine dimers caused by UV radiation. Without proper NER, individuals can show extreme sensitivity to sunlight and have a higher risk of developing skin cancers early in life.