Final answer:
The 5′ to 3′ polarity restriction causes the discontinuous aspect of DNA replication, resulting in the synthesis of the lagging strand in short fragments called Okazaki fragments.
Step-by-step explanation:
The discontinuous aspect of replication of DNA in vivo is caused by the 5′ to 3′ polarity restriction. This restriction arises from the fact that DNA polymerase can only synthesize new DNA strands in the 5' to 3' direction. As a result, when the leading strand is being synthesized continuously towards the replication fork, the lagging strand, which is complementary to the 5' to 3' parental DNA strand, is synthesized away from the replication fork in short fragments known as Okazaki fragments. Each fragment requires a primer to start the synthesis.