Electron microscopy of replication structures provides direct visualization of what?

• A. Replication fork architecture and intermediates.
• B. RNA processing events.
• C. Sequencing of genomes.
• D. Chromatin remodeling.

Answer: (A)

Electron microscopy of replication structures directly reveals the physical shape and arrangement of DNA as replication proceeds. You can see the replication fork where the two parental strands separate and new strands are synthesized—leading strand synthesis on one side and lagging strand synthesis on the other—plus intermediates like fork junctions and replication bubbles. This is why it's the best answer: EM provides a direct visual snapshot of the fork architecture and the intermediates formed during DNA replication.

RNA processing events, sequencing, and chromatin remodeling involve different aspects and aren’t the direct, visible structures captured when imaging replication. RNA processing focuses on RNA molecules and their maturation steps; sequencing is a method to determine the order of nucleotides in DNA or RNA; chromatin remodeling concerns changes in nucleosome positioning and DNA packaging—structures that are not the immediate replication fork arrangement observed by electron microscopy.