Question

What is the relation between low agarose concentration to high concentration

Answer 1

I have done these types of separation very well, this is how it worked with me, run the gel as you describe cut out the two bands neatly as clean as you can, load these cut bands with agarose again in the wells for another round of gel electrophoresis. It works great. Using lower concentrations of gel is not good because the yield of getting the DNA lowers tremendously. In other words separation of DNA from agarose gets difficult no matter what you do. You might be good with 2 or at the most 3 agarose runs sequentially but it is outstanding clean DNA in the end. Hope it works for you. Hare Krishna!