RNA sample DNA ladder- how do they correspond? - (Jan/31/2008 )

RNA and DNA travels different on an agaros-gel (not-denaturating), but how different? If I have a DNA ladder, how can I use it to find the size of my RNA band?

I have read it somewhere but I can not find it now.

Thanks!

I'm not sure you can compare non-denatured RNA to a DNA ladder.
If it was denatured, maybe you could establish some correlation by running RNA molecules of known size.
But in your case, the secondary structures can influence migration a lot. Maybe you can get an idea of how big the RNA molecules are, but I don't think it will be possible to determine the exact size...