For identifying positive clones from a plasmid cloning procedure, the routine of performing a mini-prep and then checking the putative clones by restriction digestion is most commonly used.

Of course, if you need to screen a large number of clones, another option is a colony PCR to identify positives, followed by restriction digests to confirm.

However, there is a quick & dirty screening method that is even faster than colony PCR.

Called colony cracking, it involves picking a colony straight into lysis buffer, running the extract straight onto an agarose gel, and then identifying positive clones based the electrophoretic mobility difference between the super coiled DNA with and without insert - plasmids with inserts will travel slower than plasmids without them (no-insert control).

Obviously, the larger the insert, the easier it will be to distinguish between positive and negative clones, but researchers claim to be able to detect inserts of only 200bp (see the alternate protocol links at the bottom of the page).

If you’d like to try this method, read further. Read more »

Amid growing recognition that a successful scientific career requires skills beyond scientific acumen, institutions are racing to provide management training for newly minted principal investigators. Young scientists spend years conducting complicated experiments and crunching data, but when they are finally given the keys to their own lab, they suddenly face tasks they were never trained for in graduate school.

That’s the opening snippet of the analysis article in the March 21st issue of Cell about Managing to Excel at Science.
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