You have two choices of DNA loading dye 1 bromophenol blue o

You have two choices of DNA loading dye. 1: bromophenol blue or 2: xylene cyanol FF. In TBE buffer, bromophenol blue runs at the same speed as a 370bp DNA fragment while xylene cyanol FF runs at the same speed as a 4160 bp DNA fragment. You have a PCR product which you expect to be 1000bp. Which loading dye would you use to add to your sample and run on the gel? Explain your answer.

Xylene cyanol FF TAE: 4160 bp TBE: 3030 bp Bromophenol blue TAE: 370bp TBE: 220 bp

Solution

As both dyes work at same speed and showing 2 bands , one with bromophenol blue and other with xylene cyanol.

We use bromophenol blue dye to run the gel because we want to track DNA of 1000bp

As xylene cyanol can be stag means on upper side of gel and DNA will leak out of gel and we cannot confirm whether DNA is separate or not

So answer is bromophenol blue as we want small size DNA