[BIO 1306] Ch20_Lecture

[BIO 1306] - 20 Development and Evolutionary Change 20 Development and Evolutionary Change 20.1 How Does a Molecular Tool Kit Govern Development

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20 Development and Evolutionary Change
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20 Development and Evolutionary Change 20.1 How Does a Molecular Tool Kit Govern Development? 20.2 How Can Mutations with Large Effects Change Only One Part of the Body? 20.3 How Can Differences among Species Evolve? 20.4 How Does the Environment Modulate Development? 20.5 How Do Developmental Genes Constrain Evolution?
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20.1 How Does a Molecular Tool Kit Govern Development? Developmental genes were first studied in the fruit fly, Drosophila . Using comparative genomics, scientists discovered a similar set of genes in vertebrates. The amazing diversity of organisms is produced by a modest number of regulatory genes.
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20.1 How Does a Molecular Tool Kit Govern Development? The molecular toolkit —the transcription factors, extracellular signals, and developmental genes, that govern pattern formation. A few tools can be used to build many structures.
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20.1 How Does a Molecular Tool Kit Govern Development? Plants and animals share many regulatory genes. Similar gene families, MADS in plants and Hox in animals, govern cell differentiation in similar ways. These lineages diverged in the far distant past. The regulatory genes have been conserved —they have changed little.
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20.1 How Does a Molecular Tool Kit Govern Development? The same kind of homeobox-containing genes direct the anterior-posterior axis orientation of both insect and mammalian embryos. Mutations of these genes have similar effects in both insects and mice.
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Figure 20.1 Regulatory Genes Show Similar Expression Patterns
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Figure 20.2 Altering Homeotic Genes Changes Morphology
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20.2 How Can Mutations with Large Effects Change Only One Part of the Body? Embryos are made up of modules functional entities consisting of genes, the signaling pathways the genes stimulate, and physical structures that result. The form of each module can be changed independently of other modules.
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20.2 How Can Mutations with Large Effects Change Only One Part of the Body? Genetic switches control how the molecular toolkit is used. These DNA sequences determine where and when genes will be turned on or off. Multiple switches control each gene; and most elements in the toolkit influence more than one developmental process.
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20.2 How Can Mutations with Large Effects Change Only One Part of the Body? In an embryo, genetic switches integrate positional information, and play a key role in making different modules develop differently. Genetic switches control the activity of Hox genes by activating each Hox gene in different zones of the body.
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Figure 20.3 Segments Differentiate under Control of Genetic Switches
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20.2 How Can Mutations with Large Effects Change Only One Part of the Body? Modularity also allows the timing of
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This note was uploaded on 04/08/2008 for the course BIO 1306 taught by Professor Adair,tamarah during the Spring '08 term at Baylor.

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[BIO 1306] - 20 Development and Evolutionary Change 20 Development and Evolutionary Change 20.1 How Does a Molecular Tool Kit Govern Development

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