Cellular control

• Homeobox genes


  Regulatory genes that code for proteins involved in DNA regulation, around 180 base pairs long
• Homeobox genes


  • Control development and positioning of body parts
  • Highly conserved in plants, animals, and fungi
• Example of homeobox gene

  • Pax6 gene - controls eye development
• Mitosis


  Cell division that creates genetically identical cells, crucial for growth and repair
• Apoptosis


  Programmed cell death, breaks down tissues (e.g. webbed fingers, or a tadpole's tail)
• Hox genes


  Homeobox genes found only in animals, 39 Hox genes in 4 clusters across different chromosomes
• Mutation in homeobox/Hox genes


  Can cause different body arrangements, like a double-headed cow
• Translational level of gene expression control

  Deciding whether or not to allow translation to go ahead
• Downregulating translation


  1. Degrade the mRNA

  2. Have inhibitory proteins bind to the mRNA
• Allowing translation to happen


  Activate initiation factors to allow the mRNA to bind to the ribosome
• Activation of initiation factors

  Done by phosphorylation - adding a phosphate group through protein kinases
• Protein kinases


  Can be activated by cAMP
• Post-translational control


  Modifying the protein after it has been translated
• Ways to modify proteins post-translationally

  • Add non-protein groups (e.g. carbohydrates, lipids, phosphates)
  • Modify amino acids to form special bonds (e.g. disulfide bridges)
  • Change or affect protein folding (tertiary or quaternary structure)
• Modification by cyclic AMP (cAMP)

  1. cAMP binds to CRP receptor protein

  2. cAMP-CRP complex binds to RNA polymerase to upregulate transcription and translation

  3. cAMP activates kinases which then phosphorylate and activate other enzymes and proteins