Consider a knot as being formed from two tangles.
The following three operations are called mutations.

1. Cut the knot open along four points on each of the four strings coming out of , flipping over, and gluing the strings back together.

2. Cut the knot open along four points on each of the four strings coming out of , flipping to the right, and gluing the strings back together.

3. Cut the knot, rotate it by ,
and reglue. This is equivalent to performing (1), then (2).

Mutations applied to an alternating knot projection always yield an alternating knot. The mutation of a
knot is always another knot (a
opposed to a link).