Question

List the events in order that occur at oriC to initiate DNA replication?

Answer 1

DNA replication in E. coli starts at oriC, where DNA unwinds and various proteins like helicase and topoisomerase assist in forming replication forks. This is followed by the synthesis of RNA primers, nucleotide addition by DNA polymerase III, and completion of the newly synthesized strands by DNA ligase.

Step-by-step explanation:

Events that Occur at oriC to Initiate DNA Replication

1. DNA unwinds at the origin of replication.
2. Helicase opens up the DNA-forming replication forks; these are extended bidirectionally.
3. Single-strand binding proteins coat the DNA around the replication fork to prevent rewinding of the DNA.
4. Topoisomerase binds at the region ahead of the replication fork to prevent supercoiling.
5. Primase synthesizes RNA primers complementary to the DNA strand.
6. DNA polymerase III starts adding nucleotides to the 3'-OH end of the primer.
7. Elongation of both the lagging and the leading strand continues.
8. RNA primers are removed by exonuclease activity.
9. Gaps are filled by DNA pol I by adding dNTPs.
10. The gap between the two DNA fragments is sealed by DNA ligase, which helps in the formation of phosphodiester bonds.

In prokaryotes like E. coli, DNA replication begins at a specific site on the chromosome known as the origin of replication or oriC. This process is essential for cell division and growth, ensuring that each new cell receives a complete copy of the genetic material.