nucleotides and nucleic acids

• DNA


  Carries genetic information
• RNA


  Transfers genetic information from DNA to ribosomes
• Nucleotides


  Consist of pentose (5 carbon sugar), a nitrogen containing organic base, and a phosphate group

  
• Components of a DNA nucleotide

  • Deoxyribose
  • Phosphate group
  • Adenine
  • Cytosine
  • Guanine
  • Thymine

  
• Components of an RNA nucleotide


  • Ribose
  • Phosphate group
  • Adenine
  • Cytosine
  • Guanine
  • Uracil

  
• Phosphodiester bonds


  Bonds formed in condensation reactions that join nucleotides together
• DNA molecule


  • Double helix composed of two polynucleotides joined by hydrogen bonds between complementary bases
• RNA


  • Relatively short single polynucleotide chain
• ATP


  Nucleotide derivative consisting of ribose, adenine and three phosphate groups

  
• ATP hydrolysis


  1. Energy is released

  2. Catalysed by ATP hydrolase

  3. Inorganic phosphate can be used to phosphorylate other compounds
• ATP synthesis


  1. Condensation of ADP and inorganic phosphate

  2. Catalysed by ATP synthase

  3. Occurs during photosynthesis and respiration
• DNA replication


  1. DNA helicase unwinds double helix and separates strands

  2. Complementary base pairing occurs between template strands and free nucleotides

  3. DNA polymerase joins adjacent nucleotides by phosphodiester bonds
• Genetic code


  Order of bases on DNA, consisting of triplets of bases that code for particular amino acids (codons)
• Genetic code


  • Non-overlapping
  • Degenerate (more than one triplet codes for the same amino acid)
  • Contains start and stop codons
• Transcription


  1. DNA strand is transcribed into mRNA in the nucleus

  2. RNA polymerase uses DNA template to make mRNA molecule
• Translation


  1. mRNA attaches to ribosome

  2. tRNA collects amino acids from cytoplasm and carries them to ribosome

  3. Amino acids join by peptide bonds to form polypeptide chain
• Not all the genome codes for proteins - non-coding sections are called introns, coding regions are called exons
• Mutations in DNA can alter amino acid sequence and protein structure, leading to various effects including harmful ones like cystic fibrosis and sickle cell anaemia