What is the purpose of gel electrophoresis in genetic analysis?

• A. To separate DNA fragments by size for analysis and identification.
• B. To quantify protein concentration.
• C. To separate RNA fragments by size.
• D. To amplify DNA segments for sequencing.

Answer: (A)

Gel electrophoresis separates DNA fragments by size, which is essential for analyzing and identifying genetic material. When an electric field is applied, DNA’s negatively charged backbone moves toward the positive electrode, and the gel matrix acts like a sieve. Smaller fragments slip through the pores more easily and run farther than larger ones, producing distinct bands that reflect fragment lengths. By comparing the band pattern to a DNA size ladder, you can estimate sizes and verify whether a digestion, PCR product, or cloning step gave the expected results. This method is especially useful for confirming fragment sizes after restriction enzyme cuts or for genotyping. Staining the gel with a DNA dye and visualizing under UV or blue light makes the bands visible. It isn’t used to quantify protein concentration, it’s not primarily for separating RNA fragments in standard workflows, and it doesn’t amplify DNA—those are different techniques with different purposes.