Model organisms

  1. How do animals control development?
    • Transcription activation of gene combinations in different cells
    • Activating combinations of genes in patterns controls development decisions (tissue type, cell type, cell life)
  2. Baer and Haeckel
    • Observed that embryonic stages of different vertebrates resembled each other
    • Ontogeny recapitulates phylogeny
  3. Fruit fly life cycle
    Fertilized egg > blastoderm > embryo > larva > pupo > adult fly
  4. Mutation in HOX gene in fruit flies
    • Recessive mutation in HOX gene UBX: 2 winged > 4 winged
    • Dominant mutation in HOX gene Antp: turned antennae into legs
  5. Southern Blot
    • Method for finding whether genes from one species are present in the genomes of other species
    • Have a gel where the entire genomic DNA is cut with restriction enzymes so you get a range of different fragments
    • Put gel on filter paper with salt and water -> DNA sticks to filter paper
    • Take filter and put in solution with purified probes and wash of probes that are not bound
    • Expose to x-ray film -> have bands that show you similar genes
  6. Evidence the mammals have HOX genes similar to flies
    "Zoo" southern blot
  7. Mutation of mouse Hox10a,b,c
    • Result in extra ribs in the body
    • Image Upload 2
  8. Evidence the fruit flies and mammals had a common ancester
    • Conservation of Hox gene clusters
    • Changes in localized patterns of Hox gene expression patterns are correlated with changes in animal morphology during evolution
  9. What controls the developmental patterning of limbs?
    Posterior hox genes
  10. Overlapping HOX gene expression
    • "A" cluster - activated in different zones of the limb bud proximal-distal axis
    • "D" cluster - activated in different zones of the limb bud anterior-posterior axis
  11. Synpolydactyly Syndrome
    • Either heterozygous or homozygous for a HoxD13 gene that has an expansion of Alanine codons
    • Fewer or more fingers and toes
  12. Hand-foot-genital syndrome
    • Have a stop codon in place of Tryptophan codon
    • Sequence of HoxA13 gene
  13. Other homebox gene families
    • Engrailed
    • Tinman
    • D11
    • POU
    • Paired
    • Eyeless
    • Exd/Pbx
  14. Homeobox gene that controls heart development
    • Nikx2.5 (fetal) - abnormal heart morphogenesis
    • Tinman (fly embryo) - loss of dorsal vessel and visceral mesoderm
  15. Homeobox gene that control eye development
    • Pax6 (fetal) - Aniridia in humans and small eye in mice
    • Eyeless (fly) - almost lasck all eyes
Card Set
Model organisms