Final answer:
The backbone of the DNA helix is formed by the pentose sugar and phosphate group, which together maintain the structure of the DNA's double-helix shape.
Step-by-step explanation:
In the structure of the DNA helix, the sides of the ladder, also known as the backbone, are formed by the pentose sugar and phosphate group.
Specifically, bonds created by dehydration synthesis link the pentose sugar of one nucleotide to the phosphate group of the next, establishing a structural backbone with the nitrogenous bases—adenine, thymine, cytosine, and guanine—protruding like steps of a staircase.
This backbone is crucial for maintaining the structural integrity of the double-helix formation of DNA, while the nitrogenous bases in the center form pairs, connected by hydrogen bonds, to carry the genetic information.