How quickly can E. coli replicate its DNA?

How quickly can E. coli replicate its DNA?

• A. In about 1 hour.
• B. In about 24 hours.
• C. In about 10 minutes.
• D. In about 2 days.

Answer: (A)

DNA replication in E. coli happens very quickly because the genome is copied in two directions at once from the origin. The chromosome is about 4.6 million bases, and the replication machinery adds roughly 1,000 bases per second at each replication fork. With two forks working in opposite directions, the entire genome can be copied in about 40 minutes. In fast-growing cells, new rounds of replication can start before previous ones finish, so the overall process fits into roughly an hour in typical conditions. That makes about an hour the best, practical estimate for how long it takes to replicate the DNA. The other time frames don’t line up with the genome size and the observed replication speed.

DNA replication in E. coli happens very quickly because the genome is copied in two directions at once from the origin. The chromosome is about 4.6 million bases, and the replication machinery adds roughly 1,000 bases per second at each replication fork. With two forks working in opposite directions, the entire genome can be copied in about 40 minutes. In fast-growing cells, new rounds of replication can start before previous ones finish, so the overall process fits into roughly an hour in typical conditions. That makes about an hour the best, practical estimate for how long it takes to replicate the DNA. The other time frames don’t line up with the genome size and the observed replication speed.