How does electrophoresis separate the DNA fragments in Stage 2?

• A. Move towards the anode; movement depends on charge and size
• B. The gel separates fragments purely by color
• C. Longer fragments migrate faster than shorter ones
• D. It measures DNA sequence directly

Answer: (A)

In electrophoresis, DNA fragments are driven through a gel by an electric field. DNA has a negative charge from its phosphate backbone, so it moves toward the positive electrode (the anode). The gel acts like a sieve: smaller fragments slip through the gel’s pores more easily and travel faster, while larger fragments experience more resistance and move more slowly. This combination—charge drawing the fragments toward the anode and size-based resistance in the gel—causes the fragments to separate by length. The process does not depend on color and does not sequence DNA; it simply separates fragments by size.