What purpose does staining serve in gel electrophoresis?

• A. To visualize the DNA fragments after separation.
• B. To cut the DNA into smaller pieces.
• C. To increase the speed of migration.
• D. To amplify DNA.

Answer: (A)

Staining is used to visualize DNA fragments after they have separated in the gel. DNA is colorless, so without a stain you wouldn’t see the bands that indicate fragment sizes. Dyes bind to DNA and glow under UV or blue light, making each fragment band visible. This lets you compare positions to a ladder and determine which fragments are present. Staining doesn’t cut DNA, doesn’t change how fast fragments migrate, and isn’t involved in amplifying DNA.