White colonies no insert
Posted 24 November 2010 - 02:38 PM
I'm new in molecular biology. I did a transformation and I've got white colonies which I've screened. However there is no insert in the white colonies I've picked. They are pure white (no blue in centre/light blue). I've kept the plates in 4C for 3h after 37C for 16h/overnight. Pls help.
Posted 24 November 2010 - 11:25 PM
did you check the plasmid size on a gel?
When you compare them to the empty vector (blue colony as control) you might see that your negative white colonies are a little bit smaller than the blue one.
Sometimes breaks with loss of a piece of the lac-a region occurs, leading to white colonies because the lac-a is not active anymore as it also would be when you insert your piece of interest into this region.
Posted 25 November 2010 - 03:36 AM
There are many points at which a cloning experiment can fail. Given only that you "got white colonies with no insert", all we can say is that your cloning experiment failed...