We recently bought some mice strains that need genotyping. We are currently using the DNA extraction method from Promega (lysis buffer with EDTA, overnight incubation with proteinase K, isopropanol, etc, etc). It works well sometimes, but lately we are not getting any PCR products. The last time we got a very sharp standard ladder and positive controls, but my samples are are smeared. I can not even get GAPDH. My positive control ( from the company) works well, but my samples at the same concentration do not.
I used this kit before, and had no problem, but lately it has been very frustating. Any ideas? Any new genomic DNA extraction that works better?