DNA Double Helix created entirely in Blender.

Subdivisional geometry with mostly quads.

All modifiers are left in stack and the path that deforms the dna strand is also adjustable, so this DNA strand can be animated and tweaked fully.

This is a very flexible model and can be fully used to create commercial level animations.

All objects are logically named in Outliner and the Scene is production ready.

This was created and tested in Blender 2.79. I have used Principled BSDF shader for this.