Ch 23 - Goals for Chapter 23: Population Genetics 0. Use...

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Goals for Chapter 23: Population Genetics 0. Use Hardy Weinberg law to calculate gene and genotypic frequencies 1. Understand how population size, gene flow, and mutation affect gene frequencies 2. Explain 3 ways genetic variation is maintained in populations 3. Differentiate between 3 modes of selection (directional, stabilizing and disruptive) 4. Understand why sex evolved, and how sexual dimorphism evolved 5. Know some factors that limit selection Natural Selection and Genetic Variation 6. Biologists initially rejected natural selection because of lack of genetic mechanism 7. How do variants arise, and how are they conserved? 8. Blending theory predicted loss of variation 9. Rediscovery of Mendel’s work explained conservation of discrete traits (either or like eye color) 10.Still studying continuous traits like height or weight The Modern Synthesis 0. Populations are units of evolution 1. Small differences in fitness gradually change populations 2. Population is group of inter-breeding individuals (same area and time) 3. Gene pool is number of genes (in diploid organisms, per locus = 2 x no. of individuals) 4. 2 alleles at locus determine genotype, which determines phenotype 5. Micro-evolution is change in gene (allele) frequencies through time Hardy-Weinberg Law 0. Meiosis does not change gene frequencies 1. Consider wildflower example in text 2. 500 individuals, so there will be 1000 genes or alleles in population Figure 23.4 Preservation of variation R and W are co dominant All flowers are pink heterozygotes in G2 But in subsequent generations a 1 : 2 : 1 ratio of genotypes Notice how variation is preserved (all flowers don’t become pink) Also notice how gamete (allele) frequencies don’t change because of meiosis
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Figure 23.5 The Hardy-Weinberg theorem Assume that gamete frequencies equal allele frequencies f (R) = p = 0.8 and q or f (W) = 0.2 Then f (RR) in next generation = p
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Ch 23 - Goals for Chapter 23: Population Genetics 0. Use...

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