Hox genes

Question 1

What are hox genes?

Answer 1

• often used interchangeably with homeobox genes
• one group of homebox genes that are only present in animals
• they are responsible for the correct positioning of body parts

Question 2

Where are hox genes found?

Answer 2

• found in gene clusters
• mammals have four clusters on different chromosomes

Question 3

Why is the order of hox genes significant?

Answer 3

• the order in which the genes appear along the chromosome is the order in which their effects are expressed in the organism
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Question 4

How are body plans represented?

Answer 4

• cross section of organsims
• showing the fundamental arrangement of tissue layers

Question 5

What is the difference between diploblastic animals and triploblastic animals?

Answer 5

• diplobastic animals
  
  • two primary tissue layers
• tripoblastic
  
  • three primary tissue layers

Question 6

What is a common feature of the body plans of animals?

Answer 6

• they are segmented
• multiplied over time
  
  • specialised to form different functions
    
    • e.g. hox genes in the head control the development of mouthparts

Question 7

What are somites?

Answer 7

• the individual vertebrae and associated structures have all developed from segments in the embryo called somites
• somites are directed by Hox genes to develop in a particular way depending on their position in the sequence

Question 8

WHat are the types of symmetry the body shape shows?

Answer 8

• radial symmetry
  
  • seen in diploblastic animals like jellyfish
  • have no left or right sides
  • only a top and bottom
• bilateral symmetry
  
  • seen in most animals
  • orgnasims have both left and right sides and a head and tail rather than just a top or botton
• asymmetry
  
  • seen in sponges
  • no lines of symmetry