Foundations of Clinical Genetics Practice Test

DNA is a polymer built from nucleotides, and each nucleotide has three parts: a phosphate group, a deoxyribose sugar, and a nitrogenous base. The phosphate and sugar form the backbone of the molecule, giving it a stable, repeating framework, while the bases extend inward to store genetic information. The four bases—adenine, thymine, cytosine, and guanine—pair specifically (A with T, C with G) to create the double-helix structure that encodes hereditary data.

Ribose sugar is characteristic of RNA, not DNA, so options that use ribose reflect RNA composition rather than DNA. Amino acids are the building blocks of proteins, not DNA, and lipids are a different class of biomolecules altogether.