[Campbell Biology P.469] Which statement accurately describes the movement of DNA molecules ... | Practice Question

Which statement accurately describes the movement of DNA molecules during gel electrophoresis?

  • A: Negatively charged DNA moves towards the cathode (negative electrode), and shorter molecules move faster.
  • B: Positively charged DNA moves towards the anode (positive electrode), and longer molecules move faster.
  • C: Negatively charged DNA moves towards the anode (positive electrode), and shorter molecules move faster.
  • D: Positively charged DNA moves towards the cathode (negative electrode), and longer molecules move faster.

Explanation

DNA molecules have a net negative charge due to their phosphate backbone, causing them to migrate towards the positive electrode anode in an electric field. The gel acts as a molecular sieve, and shorter DNA fragments encounter less resistance, allowing them to travel faster and farther through the gel than longer fragments.