Describe the structure of DNA.

The structure of DNA is best described as a double helix made of nucleotides. Each nucleotide consists of three components: a phosphate group, a deoxyribose sugar, and a nitrogenous base. The double helix shape consists of two strands of nucleotides that wind around each other, with the sugar and phosphate groups forming the backbone, while the nitrogenous bases face inward and pair specifically (adenine with thymine, and cytosine with guanine). This arrangement allows for the stable storage of genetic information and enables DNA to replicate and undergo transcription to produce RNA, which is essential in protein synthesis and cellular function.

In contrast, a single strand of nucleotides lacks the structural stability needed to store genetic information effectively. A triple helix of amino acids would not accurately describe DNA, as amino acids are the building blocks of proteins, not nucleic acids. A circular structure of ribonucleotides points towards RNA, which is different in composition and function from DNA, particularly due to the presence of ribose sugar and uracil instead of thymine. Thus, the identification of DNA as a double helix composed of nucleotides is fundamental to our understanding of molecular biology.