Cis and Trans Acting Elements/Sites

[rockind78]

I am a bit confused I guess about exactly what these are. If anyone could offer up an example of each, I would be very grateful. I did find this much:

http://cancerweb.ncl.ac.uk/cgi-bin/omd?query=cis+acting

[iansmith]

Monique ask the same question in this thread
http://www.physicsforums.com/showthread.php?s=&threadid=9011&highlight=cis+trans

Basically, cis is an element that is on the same DNA molecules and trans is something on a different molecules.

Best example is with the lac operon. In wild type strain, LacI and lacO are cis acting elements. If you knock-out lacI and complement the defective strain with a plasmid carrying lacI. The lacI on the plasmid is an example of a trans acting element.