Final answer:
DNA polymerase fills in the gap after damaged DNA has been removed, and DNA ligase seals the repaired strand with a phosphodiester bond.
Step-by-step explanation:
The enzyme that fills in the gap after damaged DNA has been removed is known as DNA polymerase. This enzyme adds the correct nucleotides using the undamaged strand as a template to ensure accurate base pairing. Once DNA polymerase has filled in the missing nucleotides, DNA ligase then performs the essential function of sealing the nick in the DNA backbone with a phosphodiester bond, completing the repair process. This precise mechanism is crucial for maintaining genomic integrity and preventing mutations from accumulating, which could lead to diseases such as cancer.