Overview Nitrogenous bases purines structure login to view 1 more bullet examples login to view 4 more bullets pyrimidines structure login to view 1 more bullet examples login to view 6 more bullets Nucleoside nitrogenous base + ribose Nucelotide nitrogenous base + ribose + phosphate 3'-5' phosphodiester bond connects ribose and phosphate DNA nucleotide interactions H-bonding login to view 7 more bullets melting or denaturing login to view 5 more bullets strands antiparallel right handed double helix Chargaff's rules A % = T/U % G % = C % Clinical importance anticancer drugs can intercalate DNA login to view 1 more bullet can bind DNA login to view 1 more bullet