Onelocus diploid model Goals Predict the outcome of
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One-locus diploid model Goals: Predict the outcome of selection: when will it result in fixation, when in polymorphism Understand the effect of dominance on the rate of evolution
Back to the Foré Genotype MM juvenile adult 31 4 MV 72 23 VV 37 3 If selection continues to act in the same way, what will be the outcome?
One-locus diploid model Selection acts in the diploid phase random mating, no migration, and no mutation large population
Model conditions : allele frequencies p[t] q[t] initial genotype frequencies p[t] q[t] After selection?
Genotype frequencies after selection f’(AA) f’(Aa) f’(aa)
Allele frequencies after selection f’(AA) = f’(Aa) = 100% f’(A) = 50% f’(aa) = 100% f’(a) =
One-locus diploid model p(t+1) = p(t)2 WAA + p(t)q(t)Waa p(t) 2 WAA + 2 p(t)q(t)WAa + q(t)2 Waa
One-locus diploid model Forms of selection Directional Selection: Favoring allele A Favoring allele a Heterozygote advantage Heterozygote disadvantage (Which forms of selection were present in the haploid selection model? )
Directional selection
Directional selection: terms WAA = 1 WAa = 1 + hs Waa = 1 + s s: h:
Dominance
Dominance Imagine two alleles fighting over the phenotype (in this case, fitness(: where does the heterozygote end up? WAA WAa Waa 1 1 + s/2 1+s
Dominance Imagine two alleles fighting over the phenotype (in this case, fitness(: where does the heterozygote end up? WAA 1 WAa= Waa 1+s
Dominance Imagine two alleles fighting over the phenotype (in this case, fitness(: where does the heterozygote end up? WAA WAa Waa 1 1 + hs 1 + s
Dominance Imagine two alleles fighting over the phenotype (in this case, fitness(: where does the heterozygote end up? WAA WAa 1 1 + hs Waa 1+s
Dominance Imagine two alleles fighting over the phenotype (in this case, fitness(: where does the heterozygote end up? WAA=WAa 1 Waa 1+s
Dominance example Sickle cell anemia: HH = healthy red blood cells Hh = sickle cell trait hh = sickle cell anemia Describe the dominance of H for: blood oxygen capacity? malaria resistance?
Dominance and selection p(t+1) = p(t)2 WAA + p(t)q(t)WAa p(t) 2 WAA + 2 p(t)q(t)WAa + q(t)2 Waa If A is dominant and rare: If A is dominant and common:
Selection against a common allele If WAA < WAa < Waa, selection favors the a allele
Heterozygote advantage WAa = 1; Waa = 0. 9; WAA= 0. 8 WAa > Waa; WAa > WAA
Heterozygote disadvantage WAa = 0. 9; Waa = 1. 0; WAA= 0. 95 WAa < Waa; WAa < WAA
Equilibria What are the equilibria?
Behaviour at polymorphic equilibrium
One-locus diploid model Examples: Sickle-cell anemia
One-locus diploid model Examples: Sickle-cell anemia For the Nigerian population studied: WHH = 0. 88 WHh = 1 Whh = 0. 14 What is the expected equilibrium frequency of the non-mutant allele (H)?
Readings and questions References: Mead, S. , M. P. H. Stumpf, et al. 2003. Balancing selection at the prion protein gene consistent with prehistoric kurulike epidemics. Science 300: 640 -643. Reading: Freeman and Herron, chapter 6 (chapter 5) Questions: 1. What are the relative fitnesses for the three Foré genotypes? (Use the juvenile data to estimate genotype frequencies prior to selection). What is the expected outcome of selection? Explain. 2. Imagine that a population experienced malaria but lacked the sickle -cell allele. Using the Nigerian fitness data, sketch the evolution of the population if a new sickle cell mutation arose in the population. 3. You have identified a locus that influences survival in sparrows. The relative fitnesses for each genotype are: WAA = 1. 0; WAa = 0. 9; Waa = 0. 6. Describe the relationship between the two alleles in terms of dominance.
- Predict the outcome
- Strategic goals tactical goals operational goals
- Strategic goals tactical goals operational goals
- Ocn- resonance
- General goals and specific goals
- Examples of generic goals and product-specific goals
- Therapeutic recreation models
- Produces diploid cells
- If a diploid egg was produced by mitosis
- Prophase 2
- Primary oocyte haploid or diploid
- Why is meiosis important?
- What is diploid and haploid
- Primary oocyte haploid or diploid
- Primary oocyte haploid or diploid
- Advantage of sexual reproduction
- Diplod
- Haploid diploid unterschied
- Meiosis in oogenesis
- Diploid vs haploid number
- Are diploid cells produced in meiosis
- Cell with 4 chromosomes
- Diploid cells
- Privet shrubs and humans each have a diploid number of 46
- Privet shrubs and humans each have a diploid number of 46
- Daniel svozil
- Dna structure and replication pogil