Final answer:
DNA synthesis on the leading strand occurs continuously, while on the lagging strand it occurs in short fragments called Okazaki fragments.
Step-by-step explanation:
The process of DNA synthesis occurs differently on the leading and lagging strands during replication. The leading strand is synthesized continuously in the 5' to 3' direction as the replication fork moves. On the other hand, the lagging strand is synthesized discontinuously in short stretches called Okazaki fragments. This is because DNA polymerase can only add nucleotides in the 5' to 3' direction and can only extend from a free 3' end.
On the lagging strand, a protein machine called primosome moves along in the direction of the fork movement, creating RNA primers with the enzyme primase in the 3' to 5' direction. DNA polymerase-III then adds deoxyribonucleotides at the 3' end in the 5' to 3' direction. Once the RNA primers are replaced by DNA, DNA pol I removes the primers and fills in the gaps with DNA nucleotides. Finally, DNA ligase seals the nicks between the newly synthesized DNA fragments.