Body Plans

• What do cells in developing organisms need to do?

  Differentiate and specialize for different roles
• How do cells control which genes are functioning?

  By switching on and off genes
• What determines the specific sequence of gene control?

  Transcription factors
• What are transcription factors?

  Proteins that bind to specific DNA sequences
• What is a homeobox?

  A DNA sequence coding for a protein transcription factor
• What do homeobox gene sequences regulate?

  The transcription of genes during development
• What is a homeobox gene?

  A gene containing a homeobox sequence
• Why are homeobox gene sequences highly conserved?

  They are maintained by natural selection
• What happens if mutations occur in homeobox sequences?

  They can lead to non-viable organisms
• What role do homeobox genes play in body plans?

  They control the development of body patterns
• How do homeobox genes affect organism polarity?

  They determine head and tail development
• What do homeobox genes control in segmented organisms?

  Segmentation into distinct body parts
• What do homeobox genes help develop in organisms?

  Body parts like wings and limbs
• What are Hox genes specifically responsible for?

  Controlling body plan development in organisms

  
• How many Hox genes are in the fruit fly Drosophila melanogaster?

  Eight Hox genes

  
• What do Hox genes determine along the anterior-posterior axis?

  The identity of embryonic body regions
• How are Hox genes organized?

  Into groups known as Hox clusters

  
• How many Hox clusters do vertebrates have?

  Four Hox clusters

  
• What is the relationship between Hox gene order and body regions?

  The order is directly related to body regions