Dual Enrollment Biology Practice Test 2026 – All-in-One Guide to Master Your Biology Exam Success!

In gel electrophoresis, the gel acts as a sieve that slows larger molecules more than smaller ones. DNA carries a roughly constant charge per length, so differences in charge don’t drive the separation as much as size does. Smaller fragments can navigate the gel’s pore network with less hindrance and thus migrate farther toward the positive electrode, while larger fragments are slowed and travel shorter distances. Therefore, the distance moved reflects the fragment’s size. GC content or sequence doesn’t determine mobility under standard conditions.