Knot theory provides a framework in which to understand how DNA is constructed. Biologists use the concept of colorability to study DNA stands, and differentiate between them. Additionally, the 4 Color Theorem also relates to tessellations. Tessellations are repeating patterns of shapes that fill a space. Tessellations are not only pretty, they help us understand how shapes work together.
Tessellations demonstrate the symmetry of shapes and patterns.
You could view coloring maps with four colors as a kind of tessellation problem. What repeats is the colors, rather than the shapes, but it still uses the foundations of tessellating, repetition, symmetry, and patterning. The Knot Theory Home Page - A wealth of information about knots, colorability, and DNA that is easy to understand. Mouse's Knot Theory Page - A great page for learning about knots. The Topology of DNA -Examples, pictures, and lots of information.