Final answer:
The RNA primer is the macromolecular structure used to initiate DNA synthesis during replication, which is later replaced by DNA nucleotides and sealed by DNA ligase.
Step-by-step explanation:
The macromolecular structure used as a replication primer in DNA replication is the RNA primer. Primase synthesizes an RNA primer at the origin of replication to initiate the synthesis of a DNA strand. DNA polymerases then use this RNA primer to start adding DNA nucleotides to the growing DNA chain. The RNA primers are eventually replaced by DNA nucleotides, and the gaps between the Okazaki fragments on the lagging strand are sealed by DNA ligase.
While Okazaki fragments are short stretches of DNA synthesized on the lagging strand, DNA polymerase is the enzyme that adds nucleotides to the growing DNA strand, using the RNA primer. Other enzymes such as DNA helicase and topoisomerase also play crucial roles during the replication process.