  Recent experiments on aligned DNA show hexatic order with no sign of
macroscopic chirality. I make the analogy between smectic liquid crystals and
chiral hexatics and show how the absence of chirality cannot occur in a
thermodynamic phase of chiral molecules. In addition, I discuss the microscopic
origin of chiral mesophases in liquid crystals and show that, within the
context of central forces between "atoms" on "molecules", chiral interactions
can occur only if there are biaxial correlations between the mesogens. Weak
biaxial correlations can therefore lead to small cholesteric pitches.

Condensed Matter;Chemical Physics