Lecture 4 - 1 Learning Objectives 1 2 3 4 5 Identify the 4...

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Learning Objectives 1. Identify the 4 major types of mutations, give an example and explain the mechanism and significance of each 2. Calculate allele frequencies accounting for mutation 3. Calculate expected allele frequencies at mutation equilibrium 4. Explain why allele frequencies may be higher or lower than 0.5 at mutation equilibrium. 5. Explain why mutation can act as the fuel for evolutionary change when mutation rates are slow and most mutations are deleterious. 1
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M U T A T I O N Lecture 4: Monday, Jan.13th Readings 5th ed. 5.2 Where new alleles come from 5.3 Where new genes come from 5.4 Chromosome mutations 6.4 Mutation (pp. 216-219) Readings 4th ed. 5.1 Where new alleles come from 5.2 Where new genes come from 5.3 Chromosome mutations 6.4 Mutation (pp. 210-212) 2
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Mutations A mutation is a sudden, random and heritable change in genetic material There is one other way for a species to attain new alleles; Any ideas? Important note! In most animals, only mutations in germline cells (those giving rise to gametes) will be passed on. MUTATION IS THE SOURCE OF NEW ALLELES--IT IS THE ‘FUEL OF EVOLUTION’ 3
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Mutation eats away at traits slowly generation f(A1) Consider for example, f(A1) at time 0 = p0 = 0.95 mutation rate = 10-4/locus/generation 0.7 0.75 0.8 0.85 0.9 0.95 1 0 500 1000 1500 2000 2500 3000 4
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Driving ‘forces’ in evolutionary change Evolution is a change in allele frequency in a population over time. If mutation is the “fuel” of evolution, who’s driving? The driving forces of evolution are: Natural selection Genetic drift Migration POPULATION GENETICS 5
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Types of mutations Point mutations Base substitutions (non/synonymous) Insertions and deletions Gene duplication Chromosome inversion Genome duplication Polyploidy 6
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The genetic code The genetic code is: U niversal (nearly) 20 am ino   ac ids Redundant (43 = 64) RNA sequence 7
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Original DNA strand DNA: CAA TCA GCT AGT mRNA: GUU AGU CGA UCA Amino acids: Val – Ser – Arg - Ser Mutation 1: replacement (nonsynonymous) substitution: DNA: CAA TC T GCT AGT m RNA: G UU AG    C G A UC A amino acids: Val – – Arg – Ser Mutatio n 2:  s ile nt s ite  (s yno nym o us ) s ubs titutio n:  DNA:  C AA TC G  G C T AG T     m RNA:
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