hmm.. the thing is that you should use a negative control in almost all PCRs right?
So.. if you first do a PCR, then purify the samples from all nucleotides, primers, etc that are just a contamination of the pure DNA you want to sequence it somehow makes sense to me to do a negative control to rule out possible contamination so that.. one could define the sequence of the other samples and IDK... substract the "wrong" data???
idk.. I only know that my professor insists on negative controls and I'm pretty sure it is one of the main questions on my exam next week.
Thanks for your help though......