Chapter 3 reading guide: nucleic acids and transcription. The targeted reading is created to guide your study, directing your attention to the content that will help you meet the learning objectives. There are detailed learning objectives at the end of the document if you need extra guidance. The answers to the self-assessment questions are also included. 3. 1 chemical composition and structure of dna (p. 51-57) Dna is a polymer of nucleotides that forms a double helix. Deoxyribonucleic acid (dna): a linear polymer of four subunits; the information archive in all organisms. Double helix: the structure formed by two strands of complementary nucleotides that coil around each other. Genetic information: information carried in dna, organized in the form of genes. Genes: the unit of heredity; the stretch of dna that affects one or more traits in an organism, usually through an encoded protein or noncoding rna. Gene expression: the production of a functional gene product.