What is the shape of a drop of water?

If the drop is small enough, it is a perfect sphere.
 A sphere is the geometrical shape that has the smallest surface area for its volume. The drop takes this shape because water molecules tend to stick to each other. So, when not confined by a container, and with nothing around it to distort its shape, a very tiny water drop is perfectly round like a ball because the water molecules are pulling inward toward each other. 

If the drop is larger like a raindrop in free-fall, it has a domed top and a semi-flattened bottom because as it falls it must push the air out of its way. That "upward" push of the air being displaced causes the falling drop to have a rather flattened bottom. 

Contrary to popular misconception, a free-falling raindrop is not shaped like a teardrop -- round on the bottom and pointy on top.

From:https://www.quora.com/When-a-water-drop-falls-does-it-form-a-circular-shape

Dna strands are split apart to allow an opening for replication. the opening has two replication forks so synthesis goes toward them in 5' to 3' direction.