What does the origin of replication in a plasmid enable?

• A. Replication of the plasmid within the host
• B. Integration into the host chromosome
• C. Expression of the inserted gene
• D. Protection from degradation

Answer: (A)

The origin of replication is the site that tells the host cell’s replication machinery where to start copying the plasmid. Because of this signal, the plasmid can be replicated independently of the host chromosome, producing multiple copies that are inherited by daughter cells during cell division. That happens only if the plasmid has a functional origin of replication, so it can persist in the population of cells.

Integration into the host chromosome would require recombination signals or integrase enzymes, not the replication start site. Expression of the inserted gene depends on promoter and regulatory elements, not on the origin. Protection from degradation isn’t provided by the origin; stability often involves other sequences and factors.