Topic10.pdf - Topic 10 Chromosome Variation 1 Survey the...

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Topic 10: Chromosome Variation 1. Survey the way that chromosome number can vary both within and between species. Distinguish between autopolyploidy, allopolyploidy, and aneuploidy. 2. Characterize large scale mutations, including gene duplications and deletions as well as chromosomal rearrangements, such as inversions and translocations. How might these changes contribute to the evolution of new phenotypes and/or new species? 1
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Big Question: How can large scale mutations arise and affect phenotype?
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BUT: C-some mutations have greater effect in evolution of new traits and speciation 3 Point mutations % total Missense and nonsense in protein coding 57% Change in splice site 9.6% Change in regulatory sequence 1.4% Small insertion (<20 bp) 16% Small deletion (<20 bp) 6.4% Repeat variants 0.2% Chromosomal alterations % total Large deletions 5.6% Large insertions 1% Complex Rearrangements 0.8% How often does each type of mutation result in a human disease?
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Types of Chromosomal Mutations 4
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Duplication Deletion Inversion Translocation Chromosomal rearrangements Unbalanced some loss or duplication of information Balanced no loss or duplication of information 5
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Chromosomal breaks induce rearrangements when repaired 6
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Interspersed Repeated sequence allows recombination between chromosomes Transposons Retrotransposons 7
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Duplication mutation in which part of the chromosome has been doubled – tandem duplication – Or dispersed (displaced) duplication – same or reversed order (tandem) 8
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Unbalanced duplications affect gene expression 9 Rare More frequent Existing tandem duplications result in more duplications by incorrect alignment Mutation by unequal crossing over
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