Which statement correctly describes replication origins in eukaryotes?

Which statement correctly describes replication origins in eukaryotes?

• A. There is only one origin per chromosome.
• B. Origins can be hundreds or thousands in a chromosome.
• C. Origins are randomly located and do not form bubbles.
• D. Origins are the sites where replication begins.

Answer: (C)

Replication origins are the starting points for DNA duplication. In eukaryotes, there are many origins along each chromosome, not just a single one, and these origins are licensed and activated at different times during S phase. When an origin fires, replication forks move in both directions, creating a replication bubble that expands as replication proceeds. This makes the statement that origins are randomly located and do not form bubbles inaccurate. The correct idea is that origins are the sites where replication begins, with multiple origins per chromosome driving complete and timely duplication.

Replication origins are the starting points for DNA duplication. In eukaryotes, there are many origins along each chromosome, not just a single one, and these origins are licensed and activated at different times during S phase. When an origin fires, replication forks move in both directions, creating a replication bubble that expands as replication proceeds. This makes the statement that origins are randomly located and do not form bubbles inaccurate. The correct idea is that origins are the sites where replication begins, with multiple origins per chromosome driving complete and timely duplication.