DNA replication proceeds in both directions from an origin of replication. Black arrows indicate the direction of growth of daughter DNA molecules. (a) Starting at the origin, DNA polymerases move outward in both directions. Long yellow arrows represent leading strands and short joined yellow arrows represent lagging strands. (b) How replication proceeds at the chromosome level. Three origins of replication are shown in this example.
ANIMATED ART: DNA replication: replication of a chromosome