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How then do we end up with such diversity 42613 13

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How then do we end up with such diversity?
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4/26/13 13 Homeobox ( Hox ) genes Homeotic mutations are those that transform one body part into another. These turn out to be mutations in Hox genes, which encode transcription factors. Hox genes in flies: expression patterns and gene arrangement
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4/26/13 14 Flies (Diptera) have wings on only one thoracic segment (T2) Mutations in Hox genes
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4/26/13 15 Mutations in Hox genes Mutations in Hox genes
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4/26/13 16 Mutations in Hox genes In arthropods, Hox genes control segment identity Influence basic body plans. Hox genes appear to be the major switches involved in determination of what sort of appendages occur on each segment.
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4/26/13 17 Hox genes and segmentation patterns in arthropods
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4/26/13 18 Hox genes in different animal phyla Hox genes in mouse Homologous to insect Hox genes Gene organization and expression order conserved!
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4/26/13 19 Drosophila eye • Master regulator: eyeless (Pax6) • A transcription factor, but not Hox gene What happens when eyeless is expressed in the wrong place? New eyes form! Partially functional
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4/26/13 20 What happens when eyeless is expressed in the wrong place? New eyes form! Partially functional Eyeless in mouse/human • Amino acid sequence highly conserved with flies • Over-expressing mouse eyeless in fly gives the same extra-eye phenotype! • Mutations in humans lead to aniridia Wild-type Eyeless mutant
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4/26/13 21 Macroevolution via gene expression regulation • Changes in expression patterns of master regulators can have major phenotypic effects • These regulators are conserved across all animals– since the proteins can substitute for one another, change must be in their regulation
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How then do we end up with such diversity 42613 13 Homeobox...

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