Hello! I conducted a transformation experiment and plated the bacteria on antibiotic agar with blue-white screening. The plasmid I used was a linearized T-vector. The insert with A overhangs would insert into the lacZ gene. If it is successfully inserted, white colonies should form. However, apparently it's possible to get blue colonies. I don't understand why. Can the T overhangs self-ligate somehow? Or would it be something in the preparatory steps for constructing the vector - say, the prep was not complete and some circularized plasmids remained or the t overhangs were not added successfully? I was also thinking that maybe the bacteria could remove overhangs? I included a circularized control, is it merely to cover the possibility of contamination? I personally don't think so, I had a 'blank' colony (no insert included but t-vector was), on which nothing grew. Although this doesn't actually tell me much. Anyone got any ideas. Many thanks.