Lecture 10 - Chapter 25 - Molecular Systematics

Lecture 10 - Chapter 25 - Molecular Systematics - Insights...

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Insights from Molecular Systematics 2 3 Molecular trees span both short and long periods of time because molecules evolve at different rates 4 Conserved sequences like 16s rRNA resolve deep divergences
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5 Rapidly evolving sequences like mtDNA resolve more recent divergence “mtEve” 6 Molecular phylogenies rely on two types of homologous genes: orthologous and paralogous 7 A B C D Ancestral species A B C D A B C C 1 D Species 1 Species 2 Orthologous (Used to build species trees) Paralogous (Used to reconstruct gene family expansions) (Each letter represents a gene) 8 Duplicate genes may go on to develop new functions Duplicate genes appear to play a major role in the evolution of the human brain: Fortna et al., 2004, PLoS Biology.
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9 Gene number does not predict complexity Rice: 40,000 - 50,000 Mustard weed: 25,500 Pufferfish: 21,000 Human: 20,000 - 25,000 Nematode: 20,000 10 Molecular phylogenies track evolutionary time if we assume a molecular clock 11 Molecular Clocks • The molecular clock is a yardstick for measuring absolute time of evolutionary change based on the observation that some genes and other regions of genomes seem to evolve at constant rates 12 Neutral Theory • Neutral theory states that much evolutionary change in genes and proteins has no effect on
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Lecture 10 - Chapter 25 - Molecular Systematics - Insights...

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