During replication the enzyme that forms double helix to form...

During DNA replication, helicase unwinds the DNA double helix, and topoisomerase relieves the torsional strain caused by unwinding. DNA polymerase synthesizes the new strands. On the lagging strand, DNA is synthesized in short segments called Okazaki fragments. DNA ligase is the enzyme that joins these Okazaki fragments by forming phosphodiester bonds, sealing the nicks to form a continuous daughter DNA strand, which then exists as a complete double helix.

Permease is a membrane transport protein and is not involved in DNA replication.

Answer: ligase