For RNAse containing DNA loading buffer, (for those of you that use
miniprep DNA in translations and therefore do not treat miniprep DNA with RNAse)
make as above except that you add 1/40th volume of a solution of 1 mg/ml RNAse A.
Pre-boil the RNAse A stock solution for 10 minutes to kill any contaminating
DNAse.
Nowadays it is not usually necessary to boil the RNAse A, but
every once in a while when someone is lazy and doesn't do it they no longer have
DNA in their minipreps - or worse yet it looks fine but they can't use it for
cloning!