7.3 The Structure of DNA

• Nucleotides


  • The building blocks of DNA, consisting of
  • A 5-carbon sugar (deoxyribose)
  • A phosphate group
  • One of four nitrogenous
  • Adenine (A) * Thymine (T) * Guanine (G) * Cytosine (C)
• Base pairs Complementary pairing of nucleotide bases

  - A always pairs with T

  - C always pairs with G
• Double helix


  • The overall structure of DNA
  • Two strands of nucleotides coiled around each other
  • Held together by hydrogen bonds between base pairs
• Antiparallel strands


  • The two strands of DNA run in opposite directions
  • One strand runs 5' to 3'
  • Second other 3' to 5
• Backbone


  • The outer part of the DNA molecule
  • Consists of alternating sugar and phosphate groups
• Anatomy of DNA molecule


  • Has two chains of nucleotides coiled into a double helix
  • Deoxyribose ( sugar)
  • Phosphate groups
• Chromosome


  • A structure of coiled DNA and associated proteins containing many genes.
• Gene


  • A segment of DNA that codes for a specific protein or set of proteins.
• Genome


  • The complete set of genetic instructions in an organism.