That “cos” in cosmid? Stands for – the sticky ends from lambda phage that let you pack DNA into a viral capsid.
While next-generation sequencing (NGS) has replaced many cosmid-based mapping workflows, cosmid pics remain relevant for: cosmid pics
Plus, those packaging extracts are just fun to watch. (Okay, you can’t watch them without an electron microscope, but you get the idea.) That “cos” in cosmid
| Problem in the Pic | Likely Cause | Solution | | :--- | :--- | :--- | | | Nuclease contamination or degraded DNA | Prepare fresh cosmid DNA with sterile technique. | | Very bright, high molecular weight band in the well | Genomic DNA contamination (the cosmid is stuck in the well) | Treat with RNase and clean up the prep; the cosmid should run into the gel. | | No insert release after digest | The cosmid re-ligated without an insert (empty vector) | Check the alkaline phosphatase treatment; dephosphorylate the arms. | | Fuzzy, faint bands | Not enough DNA loaded or poor stain | Load 500 ng – 1 µg of cosmid DNA; stain longer. | (Okay, you can’t watch them without an electron
Let’s be honest – you didn’t click for the definition. You want the visuals.