How do nucleotides contribute to DNA structure?

• A. By forming hydrogen bonds with each other
• B. By acting as catalysts in replication
• C. By consisting of a sugar, phosphate group, and nitrogenous base
• D. By providing energy for polymerization

Answer: (C)

Nucleotides are the fundamental building blocks of DNA, and they are composed of three key components: a sugar molecule, a phosphate group, and a nitrogenous base. The sugar in DNA is deoxyribose, and the phosphate groups link together to form the backbone of the DNA strand. The nitrogenous bases—adenine, thymine, cytosine, and guanine—extend from the sugar-phosphate backbone.

These bases pair specifically through hydrogen bonding (adenine pairs with thymine, and cytosine pairs with guanine), which contributes to the stability and structure of the DNA double helix. However, the choice regarding what nucleotides consist of directly answers how they contribute to the overall DNA structure by forming the basic framework that allows for these base pairings.

Furthermore, while nucleotides play roles in replication and energy provision, those functions are secondary to the primary structural role they serve in forming DNA. The correct answer emphasizes their composition as essential to understanding how nucleotides structure DNA.