EVE100_335-356_2pp

EVE100_335-356_2pp - 3/1/10 Genetics of speciation Many...

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3/1/10 1 335 Genetics of speciation Many plant species were formed by the hybridization of diploid species to yield a tetraploid (allopolyploid = from two species) descendant. The tetraploid mint Galeopsis tetrahit was formed by hybridization of two diploid mints. Plants resembling G. tetrahit can be created in the laboratory. Polyploid speciation in plants may be faciltiated by selFng (see ±ut pp. 396-397). 336 The X chromosome has a disproportionate effect on male hybrid sterility in Drosophila Presgraves, Trends in Genetics, 2008 Male fertility in D. pseudoobscura (white)/ D. persimilis (purple) hybrids is greatly affected by the X chromosome
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3/1/10 2 337 The X chromosome has a disproportionate effect on male hybrid sterility in Drosophila F1 females are fertile, F1 males sterile (Haldane’s Rule) Regions of D. mauritiana genome are followed though crosses by means of a transgene, found in different locations across multiple D. mauritiana lines Multiple generation backcrosses to D. simulans males result in lines that are mostly D. simulans , but have small parts of D. mauritiana genome corresponding to location of transgene Even closely related species show many incompatibilities Incompatible X chromosome introgressions are more numerous and have bigger average effects. Large-X effects may result from greater selection in males. test viability/fertility as homozygote 338 In Drosophila, the genes Ods , Hmr , Nup96, and Nup160 contribute to species incomaptibility. All show evidence of adaptive protein evolution (MK test). The agents of selection driving adaptive evolution of these genes is a
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This note was uploaded on 03/29/2010 for the course EVE EVE 100 taught by Professor Davidbegun during the Winter '10 term at UC Davis.

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EVE100_335-356_2pp - 3/1/10 Genetics of speciation Many...

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