DNA topology is the focus of an interdiscipline between molecular biology and mathematics and as a term refers to DNA supercoiling, knotting and catenation. More simply put, DNA topology studies the shape and path of the DNA helix in three dimensional space. The topology of DNA topoisomers is important to replication, transcription and recombination, including the recombination events important to the life cycles of many viruses. Topoisomerases are enzymes that change the topology of DNA.