• a number of hydrogen bonds

  • deoxyribose sugar

  • thymine base

  • phosphate group


a number of hydrogen bonds.The phosphate groups on DNA are ionic & charged. Charged molecules attract water & are hydrophilic. Each phosphate group on the DNA backbone is one unit of negative charge (-1). DNA has two hydrophilic polar external backbones made of sugars & phosphate groups joined by ester bonds.