Describe the structure of human DNA (4 marks)

- 2 strands:  Intertwine to form a double-helix structure                                                    Phosphodiester bonds between between phosphate group and pentose sugar of nucleotides                       - 4 Bases: Cytosine, Guanine, Adenine, Thymine. Complementary base pairing: A-T, C-G                                                           Hydrogen bonding between complementary bases    Extra marks (for safety): purines (A,G), pyrimidines (C,G)