Approximate rate of DNA replication in prokaryotes (nucleotides added per second per fork)

Introduction / Context:Replication speed influences cell cycle timing and genome duplication efficiency. Prokaryotic replicative polymerases are highly processive and coordinated with helicase, clamp loader, and sliding clamp, enabling rapid synthesis.

Given Data / Assumptions:

• Organism: typical bacteria such as E. coli under optimal growth.
• Metric: nucleotides incorporated per second at an active fork.
• Forks are generally bidirectional from the origin.

Concept / Approach:Experimental measurements (pulse-chase labeling, DNA fiber autoradiography) consistently place bacterial fork rates on the order of 500–1,000 nt/s per strand under good conditions. A value near 1,000 nt/s is a widely taught benchmark.

Step-by-Step Solution:Consider polymerase catalytic rate and replisome coordination.Select the standard textbook figure: ~10^3 nt/s.Reject implausibly low (10, 100) and unrealistically high (10,000, 50,000) rates.

Verification / Alternative check:Doubling times of fast-growing bacteria align with genome sizes when assuming ~1000 nt/s and two forks per origin.

Why Other Options Are Wrong:

• 10 or 100 nt/s: too slow to explain observed replication and doubling times.
• 10,000 or 50,000 nt/s: exceed known enzymatic and replisome constraints.

Common Pitfalls:Confusing eukaryotic fork rates (typically slower) with prokaryotic rates; values are organism- and condition-dependent but order of magnitude is consistent.

Final Answer:About 1,000 bases per second