Practice question

Tracking dyes are anionic dyes co-migrating with nucleic acids to visually monitor electrophoretic progress without staining DNA. Xylene cyanol FF migrates at approximately 4 kb in 1 percent agarose, while bromophenol blue migrates near 300 bp, allowing estimation for different fragment ranges. Xylene cyanol is specifically preferred for larger fragments because its slower mobility prevents premature exit. Ethidium bromide is an intercalating stain, not a front marker. TEMED is a polymerization catalyst, and agarose is the support matrix. Hence xylene cyanol serves as a reliable migration indicator.