Introduction - This script shows the structure of Z DNA. (Based on 2dcg.pdb, A.H.-J. Wang et al., Nature 282 680 (1979)).
This is Z DNA. One chain (YELLOW) runs 3' TO 5', while the other (GREEN) runs 5' TO 3' - they are antiparallel. Z DNA is left handed and the phosphate backbone is zig-zag. Z DNA has a very deep minor groove and no major groove.
Here is the cross section of Z DNA. Notice the ttight packing of the strands.