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BB lecture 2-13-09, phylogeny

BB lecture 2-13-09, phylogeny - Changes in Gene Regulation...

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Changes in Gene Regulation Changes in the form of organisms may be caused more often by changes in the regulation of developmental genes instead of changes in their sequence For example three-spine sticklebacks in lakes have fewer spines than their marine relatives The gene sequence remains the same, but the regulation of gene expression is different in the two groups of fish
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Test of Hypothesis A: Differences in the coding sequence of the Pitx1 gene? Result: No Marine stickleback embryo Close-up of ventral surface Test of Hypothesis B: Differences in the regulation of expression of Pitx1 ? Pitx1 is expressed in the ventral spine and mouth regions of developing marine sticklebacks but only in the mouth region of developing lake stickbacks. The 283 amino acids of the Pitx1 protein are identical. Result: Yes Lake stickleback embryo Close-up of mouth RESULTS Changes in Gene Regulation
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Fig. 25-25 Recent (11,500 ya) Neohipparion Pliocene (5.3 mya) Pleistocene (1.8 mya) Hipparion Nannippus Equus Pliohippus Hippidion and other genera Callippus Merychippus Archaeohippus Megahippus Hypohippus Parahippus Anchitherium Sinohippus Miocene (23 mya) Oligocene (33.9 mya) Eocene (55.8 mya) Miohippus Paleotherium Propalaeotherium Pachynolophus Hyracotherium Orohippus Mesohippus Epihippus Browsers Grazers Key
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Evolutionary “Trends” Extracting a single evolutionary progression from the
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