DNA Polymerase's 5'-to-3' Directionality
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
DNA polymerase adds new nucleotides only to a primer's or growing strand's 3' end, so synthesis always proceeds in the 5'-to-3' direction.
Show
DNA polymerase extends an existing 3'-OH end one nucleotide at a time, never building a new strand from its 5' end.
Watch for
This one-directional restriction, not any other property of the enzyme, forces the leading and lagging strands to synthesize differently.