nucleic acids

• nucleic acids:

  • DNA: deoxyribonucleic acid
  • RNA: ribonucleic acid
• DNA:

  • store genetic info
  • double helix structure
  • made of nucleotides
• RNA:

  • single stranded
  • transfer genetic info from DNA to ribosomes
  • which read RNA to make polypeptides in process- translation
  • ribosomes composed of DNA and RNA
• NUCLEOTIDES:

  these make up DNA & RNA

  made of:

  • pentose sugar: 5C atom
  • Nitrogen-containing organic base (cytosine, guanine, adenine, thymine (DNA), uracil (RNA)
  • phosphate group

  parts joined by condensation reactions and form mononucleotide

  two mononucleotide joined by condensation reaction by sugar and phosphate, forms PHOSPHODIESTER BOND, polynucleotide formed if more than two nucleotides join

  chain of sugar and phosphate: sugar-phosphate backbone
• DNA structure

  • pentose sugar: deoxyribose
  • phosphate group
  • base varies: A, T, C, G
• RNA structure

  • pentose sugar: ribose
  • phosphate group
  • base varies: A, U, C, G
• DNA double helix structure:

  • A double helix is a structure formed by two strands of polynucleotide chains held together by hydrogen bonds
  • H bonds formed between two complementary bases: A-T, C-G
  • two H bonds between A-t
  • three H bonds between C-G
  • antiparallel polynucleotide strands twist and form DNA double-helix
• RNA chain:

  • single polynucleotide chain
  • much shorter than DNA
• DNA replication:

  • by semi-conservative replication

  1. enzyme DNA helicase breaks H bonds between two polynucleotide DNA strands, DNA helix unwinds
  2. each original strand acts as a template for a new strand. complementary base pairing of free-floating DNA nucleotides attracted to complementary exposed bases in the template strand
  3. condensation reaction joins nucleotides of new strands together, catalysed by the enzyme DNA polymerase. H bonds form between bases on original and new strands
  4. each new DNA molecule contain a strand from original DNA molecule and one new strand