Which group of organisms typically has thousands of origins of replication?

• A. Bacteria
• B. Archaea
• C. Eukaryotes
• D. Viruses

Answer: (C)

The number of origins of replication scales with genome size and how the genome is organized. Eukaryotes have large, linear genomes broken into many chromosomes, so they use thousands of origins of replication to copy all DNA efficiently within S phase. In contrast, a typical bacterial chromosome is circular and has a single origin, so replication starts from one main site. Archaea often have multiple origins but far fewer than eukaryotes, reflecting their smaller genomes. Viruses usually carry compact genomes and rely on host machinery, often with just one origin or a few. Therefore, thousands of origins are a hallmark of eukaryotic genomes.