11.26.07 - Darren Rothberg Biol 105 Evolution 11.26.07...

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Darren Rothberg Biol 105 – Evolution 11.26.07 I) M UTATIONS ! (cont’d) 1) Chromosome inversions a 2 double strand breaks in chromosome (i) segment detaches, flips, reanneals (improperly/backwards) (ii) inverted sequence cannot align properly with normal homolog (iii) successful cross-over with normal homolog very rare in inverted sequence b Result: loci within inversions are inherited together as a supergene Drosophila pseudobscura Six chromosomes, 5 polymorphic for at least one inversion Frequency of some vary with climate and latitude in the Old World where the species is native Anthropogenic “Experiment” Part I Released in Chile in 1978 Spread in South America Saw same latitudinal pattern of frequency change as in the Old World Suggested similar responses to environmental selection Anthropogenic “Experiment” Part II Found in Port Angeles, Washington in 1982 Same subset of inversions as in Chile: infer, from Chile Spread in North America Produced parallel clinal variation
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11.26.07 - Darren Rothberg Biol 105 Evolution 11.26.07...

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