What is the molecular structure of DNA primarily composed of?

The molecular structure of DNA is primarily composed of nucleotides, which are the building blocks of nucleic acids. Each nucleotide consists of three components: a five-carbon sugar (deoxyribose in the case of DNA), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine). The arrangement of these nucleotides forms the long, double-helix structure of DNA, which encodes genetic information.

Nucleotides link together through phosphodiester bonds, creating the sugar-phosphate backbone, while the nitrogenous bases pair with complementary bases on the opposite strand, maintaining the structure and function of DNA in storing genetic information. This structure is key to the processes of DNA replication and transcription, essential for life and the continuity of genetic information from one generation to the next.

Other options, such as amino acids, fatty acids, and carbohydrates, do not form the structure of DNA. Amino acids are the building blocks of proteins, fatty acids are components of lipids, and carbohydrates are primarily energy sources and structural components in cells. Therefore, the composition of DNA is distinctly unique due to its nucleotide arrangement and the role it plays in heredity.