I am doing a lot of cloning at the moment and am screening my colonies by PCR. Is it necessary to use a proofreading ploymerase? Does anyone have a recommendation for something reliable and cheap?
For screening purposes, and considering that your amplicon within 1.5 kb, you need not do PCR with proofreading enzyme. Any commercially available normal Taq polymerase is Ok. Youcan get low cost Taqs from Sigma, Fermentas etc. We are using Sigma Taq polymerase (D4545-20X250UN) for our regular amplifcations including colony PCR.