DNA fiber assays provide what kind of information?

• A. Visualization of replication fork progression along individual DNA fibers, revealing replication dynamics.
• B. Bulk average replication rate across cell populations.
• C. Methylation patterns along DNA.
• D. Protein-DNA binding affinities in vitro.

Answer: (A)

DNA fiber assays visualize replication on individual DNA molecules, giving a direct view of how forks move along a strand. By labeling newly synthesized DNA with nucleotide analogs and stretching the DNA fibers, you can see the progression of replication forks, measure fork speed, and observe where origins fire or where forks stall. This single-molecule, strand-by-strand view provides detailed replication dynamics that are not captured by bulk measurements. The other options describe broader or unrelated information—bulk average replication rates across populations, methylation patterns, or protein-DNA binding affinities in vitro—not the single-fiber replication movements that this assay reveals. So, the best description is that DNA fiber assays provide visualization of replication fork progression along individual DNA fibers, revealing replication dynamics.