Which statement correctly contrasts prokaryotes and eukaryotes with respect to origins of replication?

• A. Prokaryotes Have Many Origins; Eukaryotes Have One
• B. Prokaryotes Have One Origin; Eukaryotes Have Many
• C. Both Have Equal Numbers of Origins
• D. Neither Has an Origin

Answer: (B)

The key idea here is how many starting points a cell uses to copy its DNA. Prokaryotes, with their small, usually circular genomes, start replication at a single origin and proceed bidirectionally until the entire circle is copied. This one-origin setup is enough to duplicate the genome efficiently in a simple, compact chromosome.

Eukaryotes, on the other hand, have long linear chromosomes. Replicating such large genomes quickly requires many origins of replication along each chromosome so that multiple replication forks can work at once during S phase. This ensures the entire genome is copied in a timely manner, with origins licensed and activated in a regulated pattern.

So the correct statement reflects that prokaryotes typically have one origin of replication, while eukaryotes have many origins. The other views don’t fit because prokaryotes don’t rely on many origins, and eukaryotes don’t rely on a single origin; and it’s not true that neither has an origin.