Answer: enzymes split the DNA molecule into two rails and then transport corresponding nitrogenous bases to each rail.
Explanation: enzymes perform two roles during DNA replication. first, DNA helicase splits the bonds holding the complementary nitrogenous bases together, allowing the two sides of the DNA molecule to separate. then DNA polymerase helps complementary nitrogenous bases attach to the exposed nitrogenous bases on the two strands of DNA. several other enzymes (not shown in the Gizmo) are involved in DNA replication.