The tangle model was developed in the 1980's by professors DeWitt Sumner and Claus Ernst.
This model uses the mathematics of tangles to model protein-DNA binding. An n-string
tangle is a pair (B,t) where B is a 3-dimensional ball and t is a collection
of n non-intersecting curves properly embedded in B. N-string tangles are
formed by placing 2n points on the boundary of B, and attaching n
non-intersecting curves inside B. Tangles, like knots and links, are studied through
their diagrams. In the tangle model for DNA site-specific recombination, one is required
to solve simultaneous equations for unknown tangles which are summands of observed DNA knots
and links. This discussion will give a review of the tangle model including definitions.