Which statement captures a key difference between eukaryotic and prokaryotic DNA replication?
Correct Answer: Eukaryotic chromosomes have multiple origins of replication
Introduction / Context:Genome size and chromatin organization impose distinct constraints on replication strategies in eukaryotes versus prokaryotes. Understanding origin usage and replisome dynamics is fundamental to cell biology and biotechnology.
Given Data / Assumptions:
- Eukaryotic genomes are large, linear, and packaged with histones.
- Prokaryotic genomes are typically a single circular chromosome.
- Both systems rely on priming, polymerization, and ligation.
Concept / Approach:The hallmark difference is origin usage: eukaryotic chromosomes fire many origins to complete S phase efficiently, while most bacteria use one (or very few) origins per chromosome, commonly oriC, with two forks moving bidirectionally.
Step-by-Step Solution:
Consider whether speed differences define the systems: prokaryotic polymerases are generally faster in elongation.Count polymerase varieties: eukaryotes possess many specialized polymerases; thus “fewer in eukaryotes” is incorrect.Assess primer requirement: both require RNA primers for DNA polymerases to initiate.Therefore, the accurate single best difference is multiple origins in eukaryotes.Verification / Alternative check:DNA combing and replication timing maps in eukaryotes reveal origin clusters; bacterial replication proceeds bidirectionally from oriC, supporting the stated difference.
Why Other Options Are Wrong:
- Eukaryotic polymerases faster: typically not; bacterial elongation is faster.
- Fewer polymerases in eukaryotes: opposite of reality.
- No RNA primers in eukaryotes: incorrect; primase generates RNA primers in both.
- Prokaryotes unidirectional: most are bidirectional.
Common Pitfalls:Assuming primer independence for eukaryotes or conflating number of polymerases with speed.
Final Answer:Eukaryotic chromosomes have multiple origins of replication