Which of the following is a common support medium for electrophoresis?

• A. Agarose
• B. Nitrocellulose
• C. Polyacrylamide
• D. Ethanol

Answer: (A)

Separating molecules by size in gel electrophoresis relies on a porous matrix that slows larger molecules more than smaller ones. Agarose fits as the common support medium for nucleic acids because it forms a relatively large, uniform pore network that lets DNA and RNA migrate according to size. Its concentration can be varied to adjust pore size, making it versatile for a wide range of fragment lengths. It’s inexpensive, easy to prepare, and compatible with standard buffers and stains, which is why it’s the default choice for routine DNA analysis on gels.

In comparison, polyacrylamide provides higher-resolution separation for very small fragments or proteins and requires more careful handling. Nitrocellulose isn’t a gel matrix; it’s a membrane used to transfer separated molecules in blotting procedures. Ethanol has no role as a gel medium.