5. DNA ligase
DNA ligase is the enzyme that forms Covalent Bonds between Restriction fragments.
Explanation:
The enzyme DNA ligase joins the two DNA molecules by covalent bonds. This enzyme, which the cell normally uses in DNA replication is a DNA pasting enzyme that catalyzes the formation of covalent bonds between adjacent nucleotides, joining the strands.
The result is a recombinant DNA plasmid.