(Towards understanding the processing and packaging of genetic information at the molecular level) Part I. Information content in known three-dimensional structures of nucleic acids: sequence-dependent conformation, deformation, interactions A. The classic B-DNA double helix: Watson-Crick base pair side groups vs. the polyanionic sugar-phosphate backbone B. DNA phase transitions and RNA double helices The A/B double helical transition and DNA bending Structural discriminants of A vs. B DNA Protein-induced A/B transitions The B/C double helical transition and DNA packaging Nucleosome core particle: a striking example of protein-induced DNA deformation via concerted changes in kinking and base-pair displacement Tight bending of DNA via B→A and B→C helical transitions The A-RNA double helix, including non-canonical base pairs C. Chemical basis of DNA sequence-dependent properties: structure, deformability, recognition Indirect (electrostatic) mechanism of nucleosomal DNA folding vs. sequence-dependent character of known positioning sequences Indirect recognition of sequences: pyrimidine-purine base-pair steps as sites of DNA deformability Patterns of base-amino acid contacts: direct recognition of specific DNA sequences by proteins DNA electrostatics, amino acid binding propensities, intrinsic curvature Recognition and structural roles of non-canonical base pairs