Genes & Body Plans

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  • Genes & Body Plans
    • Homeobox genes
      • They control the development of the body plan of an organism, including the polarity & positioning of organisms
      • Are expressed in specific patterns in certain stages during development of the embryo
    • How is it all controlled?
      • By homeobox genes
        • Maternal = effect genes = polarity
        • Segmentation genes = polarity of segments
        • Homeotic selector genes = identity & development of segments
      • Codes for transcription factors
      • Arranged in HOX clusters
      • Activated from anterior to posterior
    • Retinoid acid & birth defects
      • It is a derivative of Vit. A
      • Activates homeobox genes
      • It is a morphogen
      • Too much could cause cranial deformities
    • How homeobox genes work
      • Some are transcription factors & bind to genes upstream & initiate transcription
      • Sequence of base pairs produces polypeptides of about 60 AA
      • This regulates the expression of other genes
    • HOX clusters
      • Copying of HOX clusters through evolution to enable organisms of higher complexity to develop from simpler ones
      • The term refers to a group of clustered homeobox genes
        • Drosophila = 2 HOX clusters
        • Nematode = 1 HOX cluster
        • Vertebrates = 4 HOX clusters


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