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The central axis of the famous DNA double helix can become knotted or linked as a result of numerous biochemical processes, most notably site-specific recombination. Site-specific recombinases are naturally occurring enzymes that cleave and reseal DNA molecules in very precise ways. As a by product of their main purpose, they manipulate cellular DNA in topologically interesting and non-trivial ways. So if the axis of the DNA double helix is circular, these cut-and-seal mechanisms can be tracked by corresponding changes in the knot type of the DNA axis. In this talk, I'll explain several topological strategies to investigate these biological situations. As a concrete example, I will disscuss my recent work, which predics what types of DNA knots and links can arise from site-specific recombination on DNA twist knots. |