Question

What makes up the sides of the backbone of DNA?

and
What makes up the inside or the steps of a DNA molecule?

Answer 1

The backbone of a DNA molecule consists of the phosphate groups and the deoxyribose sugars, whereas the base of the DNA molecule consists of nitrogenous bases, therefore, the backbone of DNA is made up of phosphate groups and pentose sugars. Adenine is a part of the base of the molecule.

Answer 2

The sides of the backbone of DNA are made up of alternating sugar (deoxyribose) and phosphate groups. The inside of the DNA molecule, or the "steps" as you put it, consists of the bases: adenine, guanine, cytosine, and thymine. These bases pair up with each other in specific ways: adenine always pairs with thymine, and guanine always pairs with cytosine. This is what gives DNA its unique double-helical structure and allows it to store genetic information.