* Deoxyribose: This is a five-carbon sugar that provides the structural framework of the backbone.

* Phosphate Group: This is a negatively charged group that links the deoxyribose sugars together.

These alternating sugar-phosphate units create a long, continuous chain that forms the backbone of the DNA molecule. The nitrogenous bases (adenine, guanine, cytosine, and thymine) are attached to the deoxyribose sugars and project inwards, forming the "rungs" of the DNA ladder.