Question

Replication of full-length chromosome of fast growing E.coli takes

• A. lesser time than it takes E.coli to divide
• B. variable time depending on the nitrogen source of the medium
• C. longer time than it takes E.coli to divide
• D. exactly as long as it takes E.coli to divide

Answer 1

The correct option is C longer time than it takes E.coli to divide

Normally in most cases, the replication time is much shorter than the whole-cell division process of the cell. The case of E.coli is a special one, replication initiates bidirectionally from a single replication origin contained in a circular or linear chromosome. One complete replication of the chromosome takes approximately 38-40 minutes, while the cell divides every 20 mins in nutrient-rich media. This tells that the second round of replication is initiated at the two newly synthesised origins of replication of the replicating chromosome much before the completion of the first round of replication. Thus, fast dividing E.coli cells employ nested replication forks.