First we set two parameter functions of helix curves.[br]Since we know DNA is like a bond with supercoil, the two helix may not spin in mid-distance.[br]So, we definite it with a little difference.[br]That is, move one upper (or oppose) to make it a bit released[br][br]Then, draw down the basic curves.[br][br]1. cos(s+π), sin(s+π), s[br]2. cos(r), sin(r), r-1[br]3. a dot(x) on 1+ half vector to end point(x) 2, another relative dot(y) on 1+ half vector to end point(y) 2, [ t ] ( [] is floor function)[br]4. like 3 but inverse vector[br]3. & 4. are function of bases[br][br]then adapt the parameters