Despite having identical absolute configuration of all the chiral centers, DNA exists in two main conformations: right- and left-handed DNA. A and B DNA’s are right handed, while the Z-DNA is the left-handed conformation of the deoxyribonucleic acid. You can identify the handedness by fitting the right or left hand into the groove of the DNA.
The different shapes of the macromolecule allows for selective binding of stereoisomers of biologically active compounds. One example is the selective binding of the (+)-Daunorubicin to the right-handed conformation (B-DNA) and the preference of the (-)-Daunorubicin of binding to the DNA coiled in the left-handed conformation (Z-DNA).
More information in the original article: https://www.pnas.org/content/97/22/12032
DNA binding image: O. Trent, Brown Cancer Center, Department of Medicine,
University of Louisville