One way might be to get a flexible ladder and then turn both ends in opposite directions on its axis, in other words twist it. The result should be quite similar to a DNA double helix. You can use beads: http://www.instructables.com/id/The_Double_Helix_Glass_Bead_DNA_model/
DNA is a double helix made of two strands linked together with hydrogen bonds.
Double Helix
double helix
Watson and Crick
Both DNA and RNA can exist in the double helix form, but only DNA is completely stable as a double helix. The double helix RNA is usually only short "hairpin" sections folding back on itself, never the long essentially linear form of double helix DNA.
A double helix.
DNA is a double helix made of two strands linked together with hydrogen bonds.
double helix
Double Helix
double helix
double helix, twisted ladder, spiral staircase.
Watson and Crick were the first to figure out the shape of DNA, which turns out to be a double helix. They did not make it, they observed it.
the double helix refers to the SHAPE OF A DNA MOLECULE!!! It isn't that hard of a connection to make.
The double helix model became the accepted structure of DNA because it fit the experimental evidence, especially from X-ray crystallography of the DNA molecule.
Rosalind Franklin
Double helix ladder
Watson and Crick