Final answer:
A segment of DNA that undergoes replication is called a replicon, and each replicon contains an origin of replication where the replication process begins.
Step-by-step explanation:
A segment of DNA that undergoes replication is called a replicon. Each replicon contains an origin of replication. The origin of replication is a specific nucleotide sequence where the replication machinery, consisting of various proteins and enzymes, initiates the replication process. In prokaryotes like E. coli, the origin is called oriC and is about 245 base pairs long and rich in adenine-thymine (AT) pairs. In eukaryotes, which typically have much larger and more complex genomes than prokaryotes, there are multiple origins of replication along the chromosomes to ensure the entire genome can be copied in a timely manner. The process of DNA replication involves the unwinding of the DNA double helix by an enzyme called helicase, the synthesis of an RNA primer by RNA primase, and the subsequent addition of DNA nucleotides by DNA polymerases, with leading and lagging strands synthesized simultaneously yet differently due to the antiparallel structure of DNA.