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- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/08%3A_The_Response_to_Phenotypic_SelectionThe conditions for extinction are an active area of research in the field of ‘Evolutionary rescue’. More generally, for our fitness landscape result (eqn ???) to hold, an...The conditions for extinction are an active area of research in the field of ‘Evolutionary rescue’. More generally, for our fitness landscape result (eqn ???) to hold, and for us to be able to talk of our population attempting to evolve to higher mean fitness states, we need the fitness of our phenotypes to be independent of the frequency of other phenotypes in the population. (This independence allows us to assume that the fitness of individuals is not a function …
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/02%3A_Allele_and_Genotype_FrequenciesIn this chapter we will work through how the basics of Mendelian genetics play out at the population level in sexually reproducing organisms.
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/11%3A_The_Interaction_of_Selection_Mutation_and_MigrationSomewhat remarkably, the drop in mean fitness due to a site segregating at mutation–selection balance is independent of the selection coefficient against the heterozygote; it depends only on the mutat...Somewhat remarkably, the drop in mean fitness due to a site segregating at mutation–selection balance is independent of the selection coefficient against the heterozygote; it depends only on the mutation rate . Intuitively this is because, given a fixed mutation rate, less deleterious alleles can rise to a higher equilibrium frequency, and thus contribute the same total load as more deleterious (rarer) alleles, but this load is spread across more individuals in the population.
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/12%3A_The_Impact_of_Genetic_Drift_on_Selected_AllelesOver roughly the past ten thousand years, adaptive alleles conferring resistance to malaria have arisen in a number of genes and spread through human populations in areas where malaria is endemic . On...Over roughly the past ten thousand years, adaptive alleles conferring resistance to malaria have arisen in a number of genes and spread through human populations in areas where malaria is endemic . One particularly impressive case of convergent evolution in response to selection pressures imposed by malaria are the numerous changes throughout the G6PD gene, which include at least 15 common variants in Central and Eastern Asia alone that lower the activity of the enzyme . These alleles are now f…
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/06%3A_Neutral_Diversity_and_Population_StructureWe’ll now turn to consider divergence among more closely related populations. In thinking about the coalescent within populations we made the assumption that any pair of lineages is equally likely to ...We’ll now turn to consider divergence among more closely related populations. In thinking about the coalescent within populations we made the assumption that any pair of lineages is equally likely to coalesce with each other. However, when there is population structure this assumption is violated, as the parent for an allele is likely to be found in the same population as it’s child and so lineages in different populations are less likely to coalesce.
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/05%3A_The_Population_Genetics_of_Divergence_and_Molecular_SubstitutionWe can think of the underlying gene genealogy at our gene, see Figure ???, with the total time on the coalescent genealogy within the species as Ttot and the total time for fixed ...We can think of the underlying gene genealogy at our gene, see Figure ???, with the total time on the coalescent genealogy within the species as Ttot and the total time for fixed differences between our species as T′div, note that T′div is the total time where a an allele that would appear as a subsitution could arise.
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/15%3A_An_Introduction_to_Mathematical_ConceptsThe derivative f′(a) of a function f(x) at x = a represents the instantaneous rate of change of the function, df(x), at x = a or, equivalently, the slope dx of the graph of the function at x = a. In o...The derivative f′(a) of a function f(x) at x = a represents the instantaneous rate of change of the function, df(x), at x = a or, equivalently, the slope dx of the graph of the function at x = a. In our physical example, the second derivative with respect to time is the (instantaneous) acceleration of the car, as it is the rate of change in the speed of the car (signed by whether it’s accelerating in a positive or negative direction).
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/14%3A_Interaction_of_Multiple_Selected_LociAB, haplotype 1) is determined by the interplay of two factors: First, the extent to which the marginal fitness of our haplotype is higher (or lower) than the mean fitness of the population (the magni...AB, haplotype 1) is determined by the interplay of two factors: First, the extent to which the marginal fitness of our haplotype is higher (or lower) than the mean fitness of the population (the magnitude and sign of (ˉw1−ˉw)/ˉw). After the the loss of the least deleterious haplotype, we have ratcheted up the mean deleterious mutations in the population and ratcheted down the mean fitness of the population.
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/10%3A_One-Locus_Models_of_SelectionIf the frequency of A1 is above the equilibrium frequency, then the marginal fitness of allele A2 is higher than the marginal fitness of allele A1 (ˉw1<ˉw2) and the re...If the frequency of A1 is above the equilibrium frequency, then the marginal fitness of allele A2 is higher than the marginal fitness of allele A1 (ˉw1<ˉw2) and the regression of fitness on the number of copies of allele A1 that individuals carry is negative.
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/04%3A_Genetic_Drift_and_Neutral_DiversityGenetic drift can play a role in the dynamics of all alleles in all populations, but it will play the biggest role for neutral alleles. A neutral polymorphism occurs when the segregating alleles at a ...Genetic drift can play a role in the dynamics of all alleles in all populations, but it will play the biggest role for neutral alleles. A neutral polymorphism occurs when the segregating alleles at a polymorphic site have no discernible differences in their effect on fitness. We’ll make clear what we mean by "discernible" later, but for the moment think of this as "no effect" on fitness.
- https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/16%3A_BibliographyJ a m e s, and o t h e r s, 2015 Extraordinary genetic diversity in a wood decay mushroom. Mazumdar, P., 2005 Eugenics, human genetics and human fail- ings: the Eugenics Society, its sources and its c...J a m e s, and o t h e r s, 2015 Extraordinary genetic diversity in a wood decay mushroom. Mazumdar, P., 2005 Eugenics, human genetics and human fail- ings: the Eugenics Society, its sources and its critics in Britain, Chapter Ideology and method: RA Fisher and Research in Eugenics. Ponting, and G . L u n t e r, 2014 8.2% of the human genome is constrained: variation in rates of turnover across functional element classes in the human lineage.
