Introduction - This script shows the structure of B DNA. (Based on 1bna.pdb, H.R.Drew et al, Proc. Nat. Acad. Sci USA 78 2179 (1981)).
This is B DNA. One chain (YELLOW) runs 3' TO 5', while the other (GREEN) runs 5' TO 3' - they are antiparallel. Note the wide major goove and thin minor groove.
Here is the cross section of B DNA. Note how tightly packed the core is.