\indent the central axis of the famous dna double helix is often topologically constrained or even circular. the topology of this axis can influence which proteins interact with the underlying dna. subsequently, in all cells there are proteins whose primary function is to change the dna axis topology -- for example converting a torus link into an unknot. additionally, there are several protein families that change the axis topology as a by-product of their interaction with dna. this talk will describe typical dna conformations, and the families of proteins that change these conformations. i'll present a few examples illustrating how dehn surgery methods have been useful in understanding certain dna-protein interactions, and discuss the most common topological techniques used to attack these problems.