W2L3 - DNA structure and composition

• DNA discovery:

  • 19th century - careful analysis led to discovery of chromosomes
  • Biochemical analysis showed chromos were made from DNA
  • Four runners
  • Wilkins purifies the DNA
  • Franklin did crystallography
  • Watson and crick solved structure and published in 1953
• DNA structure:

  • macromolecule
  • 2 polynucleotide chains
  • Structure has minor and major grooves
  • Types of double helical structure
  • Right handed helices
  • A DNA (11 base pairs per turn)
  • B DNA (10 base pairs per turn) - usual form
  • Left handed helices
  • Z DNA (12 base pairs per turn)
• DNA molecule structure:

  A) major

  B) minor

  
• Chemical components of DNA:

  • Nucleotide = base + ribose + phosphate
  • Nucleoside = base + ribose
  • Phosphates form phosphodiester bonds between nucleotides
  • Bases
  • Adenine (A), Guanine (G), Cytosine [C], Thymine (T) and Uracil (U in RNA)
  • 5th base is methylcytosine
  • 6th base is hydroxymethylcytosine ( involved in regulation of DNA folding through methylation )
  • Double helix
  • Sugar phosphate backbone has strong covalent bonds
  • Paired bases have weak hydrogen bonds (2 in A-T, 3 in C-G)
• Deoxyribose sugar:

  • pentose ring sugar

  A) phosphate

  B) deoxyribose

  
• Nucleotides:

  • base + ribose = nucleoside
  • base + ribose + phosphate = nucleotide

  A) sugar phosphate backbone

  B) hydrogen bonds

  
• Bases summary:

  A) purines

  B) pyrimidines

  C) guanine

  D) thymine

  E) adenine

  F) cytosine

  G) uracil

  
• Bases:

  • purines
  • double ring structures
  • adenine and guanine
  • pyrimidines
  • single ring structures
  • cytosine, thymine and uracil
• DNA nomenclature:

  • 5' and 3' ends
  • 5' is the phosphate
  • 3' is the OH
  • "antiparallel"
  • 5' to 3' strand
  • 3' to 5' strand
  • RNA
  • 5' to 3' is the direction of synthesis for new RNA

  
• DNA nomenclature:

  A) 5'

  B) 3'