What is the function of the origin of replication (ORI)?

What is the function of the origin of replication (ORI)?

• A. It is the site where transcription starts.
• B. It is the site where DNA replication begins.
• C. It is where RNA primer is laid down.
• D. It is the site where telomeres are formed.

Answer: (B)

The key idea is that the origin of replication is the starting point for copying the genome. It’s the specific DNA sequence where initiator proteins bind, unwind the DNA, and recruit the replication machinery to form a replication bubble. From this site, DNA synthesis proceeds in both directions to copy the entire chromosome. Transcription starts at promoter regions, not at the origin. RNA primers are laid down by primase at the replication forks after unwinding has begun, not at the origin itself. Telomeres are formed at the ends of linear chromosomes by telomerase and related processes, not at the origin. So this site uniquely marks where replication begins and nucleates the entire copying process.

The key idea is that the origin of replication is the starting point for copying the genome. It’s the specific DNA sequence where initiator proteins bind, unwind the DNA, and recruit the replication machinery to form a replication bubble. From this site, DNA synthesis proceeds in both directions to copy the entire chromosome. Transcription starts at promoter regions, not at the origin. RNA primers are laid down by primase at the replication forks after unwinding has begun, not at the origin itself. Telomeres are formed at the ends of linear chromosomes by telomerase and related processes, not at the origin. So this site uniquely marks where replication begins and nucleates the entire copying process.