There is a definite region in DNA where the replication originates called as origin of replication, For long DNA molecules since the two strands of DNA cannot be separated in its entire length, the replication occurs within a small opening of the DNA helix, referred to as replication fork. The DNA dependent DNA polymerase, catalyze polymerization only in one direction, that is 5' ---> 3', on one strand (the template with polarity 3' ---> 5') the replication is continuous, while on the other (the template with polarity 5' ---> 3;) it is discontinuous. The discontinuous synthesized fragments are later joined by the enzyme DNA ligase.