B-DNA:

Most common and biologically relevant form of DNA found in living organisms.

It is a right-handed helical structure with a well-defined and regular geometry.

The B-form is the typical conformation of DNA under normal cellular conditions.

A-DNA:

A-DNA is a more compact and slightly wider helical structure compared to B-DNA.

It can be induced under certain conditions, such as dehydration or in the presence of specific ions.

Z-DNA:

Z-DNA has a left-handed helical structure,

It is characterized by a zigzag or "Z" shape.

Learn: RNA Synthesis (The Living Cell)