Genetic of Development

• what are are stages of cell development?

  Undifferentiated -> determined -> differentiated
• what is determination?

  The process that leads up to the observable differentiation of a cell
• what do differentiated cells express?

  Different sets of genes
• How is diferetiation achieved?


  Through transcriptional regulation - involving gene cascades
• what is the first gene in the gene cascade called?

  master regulatory gene
• what are types of precursor cell?

  master regulatory gene, cell-specific genes
• what are the order of cell?

  Precursor cell -> determined cell -> differentiated cell
• what is turned on in a precursor cell?

  nothing both master regulatory gene and Cell-specific gene are turned off
• What are turned on in a determined cell?

  Master regulatory gene
• what are turned on in a differentiated cell?

  Master regulatory gene and Cell-specific gens
• Describe the determination and differentiation of muscle cells

  • Muscle cells develop from embryonic prcursor cells with the potential to develop into a number of different cell types
  • Signals from other cells lead to activation of the myoD master regulatory gene encoding the MyoD transcription factor
  • Cell determination has now occurred and the cells are called myoblasts
  • MyoD activates the expression of other muscle-specific transcription factors
  • These in turn activate genes for muscle protei (such as myosin) and block cell division - non-divodong myoblasts fuse to form muscle fibres
• what are the 3 main phases of drosophila development?

  Establishing the main axes

  Establishing the segments

  Filling in the details
• what is the bicoid mutants?

  An abnormal larva that has no anterior end, just two posterior ends
• what is bicoid an example of?

  Egg polarity
• what parent is responible for biocid gene?

  Defect in maternal gene
• How is bicoid formed?

  Encode proteins or mRNAs that enter the eggs while it is still in the ovary,

  When the maternal gene is defective, the egg fails to develop normally,

  Encode transcription factors which initiate a cascade of gene activation
• when is the gradient of bicoid mRNA established?

  In the unfertilized egg
• what does the Bicoid protein gradient determine?

  The anterior end of the fly
• what initiates a cascade of gene activation?

  Transcription factors
• What can determine the polarity and position?

  Established the principle that a gradient of morphogens
• what are the 3 classes of segmentation gene?

  Gap genes

  Pair-rule genes

  Segment polarity genes
• Describe the gene cascade that regulates drosophila development

  1. Egg polarity gene: Determine the anterior-posterior axis and induce...
  2. Gap genes: Subdivide the embryo into broad areas and induce...
  3. Pair-rule genes: Estalish pairs of segments and induce...
  4. Segment polarity genes: The anterior-posterior axis of each segment and induce homeotic genes
• A mutation in which gene leads to a phenotype where part of the embryo is missing?

  Gap genes

  e.g Kruppel
• what is a ultrabithorax mutant?

  A homeotic mutant that has an extra pair of wings instead of halteres.

  • The 3rd thoracic segment has been replaced by another copy of the 2nd thoracic segment
• What are homeotic genes?

  Genes that control the development of anatomical structures in an organism.
• What is antennapedia?

  legs develop in place of antennae
• What gene in drosophila determines the identity of embryonic regions along the anterior-posterior axis?

  Hox genes
• What do Hox genes encode?

  Transcription factors with a conserved DNA binding domain (homeobox)
• Where do Hox genes occur?

  in clusters, arranged in the same order as the region they affect (colinearity)
• Are flies and mammals Hox genes similar?

  Yes, enough to be swapped and still functional
• What is Hox gene important evolution role?

  Differences in morphology between species/phyla