DNA has two complementary strands that form a double helix.
The structure of DNA is called a double helix. It looks like a ladder that has been twisted at the top and the bottom. It is twisted to the right and has both major (large) and minor (small) grooves. The major groove is where the DNA backbones lie far apart; the minor groove is where they lie close together. DNA is composed of three main parts:
- a 5-carbon sugar called deoxyribose
- a phosphate group
- a nitrogenous base