what makes dna acidic

DNA is acidic because of the phosphate groups in its sugar-phosphate backbone. These phosphate groups are derived from phosphoric acid (H3PO4) and can readily donate protons (H+ ions) in solution, which is a characteristic of acids. Although DNA also contains basic nitrogenous bases, the acidic nature of the phosphate groups dominates, making DNA overall acidic and negatively charged in aqueous environments. This acidity is why DNA solutions typically have a pH less than 7.