DNA And Biotechnology Practice Test

Gel electrophoresis separates DNA fragments by size as they migrate through a gel under an electric field. DNA carries a negative charge, so when current is applied, fragments move toward the positive electrode. The gel’s porous matrix acts like a sieve, slowing larger fragments more than smaller ones, so fragments separate by length and appear as bands. By comparing to a ladder of known sizes, you can estimate the length of each piece. After running, the gel is stained to visualize the DNA bands under UV or blue-light illumination. This technique is routinely used to check PCR products, analyze restriction digests, and isolate specific fragments by excising the bands. The other options describe PCR amplification, transcription, and protein purification, which are not the goals of gel electrophoresis.