structure of DNA 1

• DNA


  Double helix consisting of 2 long chains (the lead and lag strands)
• Components of a nucleotide

  • Deoxyribose sugar
  • Phosphate
  • Nitrogenous base
• Nitrogenous bases


  • Adenine
  • Thymine
  • Guanine
  • Cytosine
• Lead strand


  Runs in a 5' end (top) to 3' end (bottom) direction
• Sugar-phosphate backbone


  The backbone of DNA
• Hydrogen bonds


  • Form between complementary base pairs
  • Weak
• DNA structure


  1. Phosphate group exposed on the 5'

  2. Deoxyribose sugar exposed on the 3'

  3. One strand runs 5' to 3'

  4. Opposite strand runs 3' to 5'

  5. Antiparallel structure forming the double helix
• Genetic code


  The sequence of bases on DNA
• Prokaryotes


  • Have a single, circular chromosome
  • Contain small circular plasmids
• Eukaryotic cells


  • Contain linear chromosomes tightly coiled around histone proteins
  • Contain small circular chromosomes in the mitochondria and chloroplasts
• Yeast is described as a special example of a eukaryote as it also contains plasmids