According to Phoebus Levene, what is DNA composed of?

DNA, or deoxyribonucleic acid, is fundamentally composed of nucleotides. Each nucleotide, which is the building block of DNA, contains three components: a phosphate group, a deoxyribose sugar, and a nitrogenous base (adenine, thymine, cytosine, or guanine). This nucleotide structure is crucial for the encoding of genetic information and the formation of the DNA double helix.

While other options such as amino acids, proteins, and polysaccharides are essential macromolecules in biology, they do not play a role in the composition of DNA. Amino acids are the building blocks of proteins, while polysaccharides are long chains of sugar molecules that perform different functions in organisms. Therefore, the recognition that nucleotides form the foundational units of DNA is central to understanding genetics and molecular biology.