DNA replication occurs ___ in eukaryotes, ____ in prokaryotes.

• A. Slow; Fast
• B. Fast; Slow
• C. Equal; Equal
• D. Variable; Variable

Answer: (A)

DNA replication speed is shaped by how genomes are organized and regulated. In eukaryotes, DNA is wrapped in chromatin with histones, and replication begins at many origins that are carefully licensed and timed during the S phase. The need to unwind, remodel chromatin, and coordinate these many origins slows fork progression, and the large eukaryotic genomes mean replication takes longer overall. In contrast, prokaryotes typically have a single circular chromosome with a simpler, chromatin-free DNA, so replication can proceed more quickly from one origin and finish faster under favorable conditions. Because of these differences, replication is slower in eukaryotes and faster in prokaryotes.