The sides of a DNA molecule are made up of two long chains of alternating sugar (deoxyribose) and phosphate groups. These chains run in opposite directions, forming a sugar-phosphate backbone.

Here's a breakdown:

* Deoxyribose: A five-carbon sugar that forms the backbone of DNA.

* Phosphate group: A negatively charged group that links the deoxyribose sugars together.

These two components alternate, forming a strong, stable structure for the DNA molecule. The bases (adenine, guanine, cytosine, and thymine) attach to the deoxyribose sugars, forming the rungs of the DNA ladder.