I have some old Lego Znap. It was part of a Lego experiment to compete with K'Nex. Its not much use and after having a look in one of the science catalogs selling K'Nex as a DNA molecule I thought I would have a go making a DNA strand with it
Here are the results. an 8 base pair set - I didn't have any more connectors. The set can be twisted into a double helical structure and since the stuff was just lying around it has found a good use.
The Znap has four colours here red - green and black - yellow making the different base pairs.
It will do until I can get a much better model and that won't be K'Nex either.