I’m not entirely sure I follow the double/single helix debate here. But for potential clarification, and to add some more types of illustration, here are some models of A- B- and Z- dna in spacefill and wireframe, both from the sideand from the http://web.virginia.edu/Heidi/chapter12/Images/8883n12_13_b.jpg.
ETA: Unfortunately, Punoqllads, it looks like google led you to a crank. That whole article seems to be by a guy who doesn’t like the fact that DNA doesn’t have the structure he thinks it should. Well, that’s nice, but he needs a hell of a lot more than that to refute decades of crystal structure determinations.
You can describe the different pictures by the difference in angle between the two strands. In the OP, the first has them arranged symmetrically, 180 degrees from each other. In the second, the angle difference is only 90 degrees, or maybe less. In Terminus Est’s B-DNA link, they look like they’re maybe 120 degrees apart. The A-DNA looks closer to 180.
It seems like this angle should be able to be determined from the data in the table in the A-DNA link.
ETA: Interesting about the A-DNA, B-DNA and Z-DNA forms. Never came across that before.
I have always wondered this also. lazybratsche’s illustrations seem to show the Z DNA with the ‘spokes crossed at the central axis’ version of the double helix.
The two versions of double helix seem to be merely an issue of phase. Sitnam would it be possible for you to explain or find an illustration of what you mean by a second axis? It seems to me that in both versions, both helix are twisting around the same axis. Looking down on a double helix from the top we see a circle with spokes. In one version the spokes cross at the axis or center of the circle. In the other extreme (ladder wrapped around a cylinder) the spokes do not cross at the central axis and the double helix is hollow. The difference between the A DNA and the B DNA helix seems to be the extent of the center hollow.
If there were two axis would we not see two circles looking down from the top? Is there another configuration I am not visualizing?
