FAQ: Why is the 10bp fragment fainter than the other fragments?

Even though the DNA mass per band is higher for the 10 bp fragment than the other fragments, it will appear fainter on the gel, due to the fact that very small DNA fragments do not bind intercalating agents as well as others, that they diffuse a lot more throughout the gel matrix, and that the charged intercalating agents (ethidium bromide or others) will run in opposite direction in the gel.