Where does DNA replication initiate and in which direction does it proceed?

Where does DNA replication initiate and in which direction does it proceed?

• A. Replication begins at a single origin and proceeds in both directions.
• B. Replication begins at random points and proceeds in a single direction.
• C. Replication begins at the ends of the molecule and proceeds toward the center.
• D. Replication begins at multiple origins scattered along the molecule and proceeds linearly.

Answer: (A)

DNA replication starts at a defined origin of replication and, in typical prokaryotes, proceeds bidirectionally from that spot. From the origin, two replication forks move in opposite directions around the chromosome, unwinding the DNA and synthesizing new strands in the 5′ to 3′ direction. This setup allows the genome to be copied quickly and efficiently, with one strand made continuously toward the fork (leading strand) and the other made in fragments away from the fork (lagging strand). The idea that replication begins at a single origin and proceeds in both directions captures the standard, widely taught model for how genomes are copied.

DNA replication starts at a defined origin of replication and, in typical prokaryotes, proceeds bidirectionally from that spot. From the origin, two replication forks move in opposite directions around the chromosome, unwinding the DNA and synthesizing new strands in the 5′ to 3′ direction. This setup allows the genome to be copied quickly and efficiently, with one strand made continuously toward the fork (leading strand) and the other made in fragments away from the fork (lagging strand). The idea that replication begins at a single origin and proceeds in both directions captures the standard, widely taught model for how genomes are copied.