Hey Cecilia,

I did not close your post, but Biostars is a Bioinformatics Q&A, not wetlab.

Having said that, I can answer your question:

Loading dye is just a mixture of a weakly-ionic dye, and something water-soluble and heavy - often glycerol or sucrose.

The idea is that the DNA gets mixed in with these heavier elements and pulled down to the bottom of the well when the mixture is loaded. Given enough time the DNA, sucrose/glycerol, and dye will all separate out into their appropriate density layers, so its important to mix it well before adding it to the gel, then lock it into the gel matrix by applying current as soon as possible (preventing the DNA/dye from diffusing around).

The ratios should not matter too much at all, since the glycerol/sucrose never make it into the gel, and the dye is very small and travels in front of any DNA (doesnt block it). The most important thing is that its consistent between experiments. I would recommend that it should be the same as whats in the ladder, assuming the ladder has your own loading dye. If your ladder comes with a loading dye already, and thats 1:5, that information is pretty much irrelevent without knowing what is in the dye, which most companies wont tell you. In short, dont worry about it. If your stuff is floating, check your TBE/TAE buffer is correct, be quicker at turning the current on, and as a last resort add sucrose/glycerol to your buffer.