Section 2: Structure of DNA Function: Stores and transmits genetic information. Structure: • Type of organic macromolecule = nucleic acid • Polymer = polynucleotide • Monomer = nucleotide Each nucleotide contains 3 parts: 1. Sugar (deoxyribose) 2. Phosphate group 3. Nitrogen-containing base Phoebus Levene Studied composition of DNA in the early 1900’s Determined it was made up of three basic pieces Structure of DNA DNA has 4 different nitrogenous bases What is the structural difference between purine and pyrimidine bases. Chargaff • Analyzed the percentage of each base in a strand of DNA. • His results: – The amount of adenine is equal to the amount of thymine – Cytosine is equal to guanine – Why did he get these results? Structure of DNA Complimentary Base Pairing • Adenine (A) always bonds with Thymine (T) • Guanine (G) always bond with Cytosine (C) Hydrogen Bonding • What is a hydrogen bond? • Hydrogen bonds hold the two strands of the DNA molecule together • There are 3 bonds between C and G • There are 2 bonds between A and T