What is the purpose of the gel loading dye containing glycerol or sucrose?

What is the purpose of the gel loading dye containing glycerol or sucrose?

• A. To fluoresce under UV light.
• B. To weigh the sample so it sinks into the well and to help monitor migration on the gel.
• C. To change the pH of the sample.
• D. To increase the DNA length.

Answer: (B)

The key idea is that loading dye is there to make the sample easy to load and to track its movement during electrophoresis. Glycerol or sucrose increases the density of the sample so it sinks into the well rather than floating away in the buffer. At the same time, the dye provides a visible marker that travels through the gel, allowing you to monitor how far the DNA has migrated. This combination lets you load samples reliably and judge when the run is complete. The glycerol/sucrose isn’t meant to make DNA fluoresce, change the pH, or increase DNA length.

The key idea is that loading dye is there to make the sample easy to load and to track its movement during electrophoresis. Glycerol or sucrose increases the density of the sample so it sinks into the well rather than floating away in the buffer. At the same time, the dye provides a visible marker that travels through the gel, allowing you to monitor how far the DNA has migrated. This combination lets you load samples reliably and judge when the run is complete. The glycerol/sucrose isn’t meant to make DNA fluoresce, change the pH, or increase DNA length.