DNA structure + scientists

• Rosalind Franklin


  British Chemist
• Maurice Wilkins


  British physicist
• Francis Crick

  British physicist
• James Watson

  American Biologist
• Rosalind Franklin worked with Maurice Wilkins to take photo of DNA structure (double helix) using X-ray diffraction
• Watson and Crick used Franklin's photo to build a model of DNA and its components
• Why do we study DNA?

  central importance to all life on Earth, medical benefits like cures for diseases, better food crops
• Our genes are on our chromosomes, which are made of a chemical called DNA
• DNA coils around histone proteins, which together form a nucleosome. They group into chromatin fibers to supercoil into a chromosome
• Nucleotides are subunits of nucleic acid, made of a Phosphate group, 5- carbon sugar, and a nitrogenous base
• DNA stands for Deoxyribonucleic Acid
• The backbone of the molecule is made of alternating phosphates and deoxyribose sugar. The teeth/rungs are nitrogenous bases
• Pyrimidines are single ring bases


  Cytosine, Thymine, Uracil
• Purines are double ring bases


  Adenine, Guanine
• DNA is a long polymer -> long chain of repeating attached molecules
• Shape of DNA

  twisted ladder or double helix
• Adenine pairs with Thymine by 2 hydrogen bonds
• Cytosine pairs with Guanine by 3 hydrogen bonds
• Nucleotides along each strand are connected by covalent bonds
• Chargaff's rule


  the bases with similar amounts always pair together
• Bases attract to each other by hydrogen bonds
• Top rail is oriented 3' to 5'

  Bottom rail is oriented 5' to 3'
• covalent bonds are found between sugar phosphate and sugar base