What information does agarose gel electrophoresis provide about DNA samples?

• A. DNA sequence information.
• B. Protein size.
• C. Fragment sizes relative to ladder and presence of multiple bands.
• D. Fragment sizes compared to ladder and presence/absence of multiple bands indicating fragment length and purity.

Answer: (D)

Agarose gel electrophoresis lets you see the sizes of DNA fragments and how many distinct pieces are present in a sample. By running the DNA alongside a ladder with known fragment lengths, you can estimate the size of each fragment based on how far it migrates in the gel. The pattern of bands tells you about fragment length distribution and purity: multiple bands mean there are several different fragments or partial digestion, while a single clean band suggests a uniform fragment length and higher sample integrity. It can also reveal if DNA is degraded or if there are contaminants that affect migration, which would show up as smearing or unexpected bands. This method does not provide sequence information and does not measure protein size.