I have been having a problem where I have isolated DNA from dna prep, nanodropped the sample to confirm actual presence of DNA and absence of contaminants, then ran on a gel and had really huge blotchy bands show up far under my ladder. I believe i have figured out that I have dnase contamination which is chopping up my plasmid. I was wondering if anyone had an idea of the source of dnase contamination???????
all glass & plastic was sterile
ligation was good
plasmid was amp/carb resistant and colonies were selected
colonies were grown overnight w/ antibiotic
miniprep was done (all reagents were new and have worked with other lab workers preps)
dna was ran on a 1% gel, plasmid expected to run around 9kb
gell ran showing ladder showing control vector plasmid but sample plasmid band ran below the 1kb ladder under 500bp
I am going to try a phenol/chloro extraction. Again, I am just wondering if anyone has any idea about how dnase contaminated my sample!?