What is A DNA?
A-DNA is a form of double-stranded DNA stable under dehydrated conditions, found in crystals and solutions with higher salt concentrations or alcohol in the solute.
Different from B-DNA
It has a more compact helix than B-DNA with a deep, narrow major groove, a wide, shallow minor groove, and a hollow center.
DNA:RNA complexes and double-stranded RNAs also take this form.