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Hardy-Weinberg Lab Notebook -Due Monday, February 10th Title/Date

Hardy-Weinberg Lab Notebook -Due Monday, February 10th Title/Date Prelab (key concepts, materials, expected outcomes)  Key concepts: equations, 5 requirements for equilibrium, etc. 3) Purpose 4) Procedure , Hypotheses x3 (for each “case” that we complete,)

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Hardy-Weinberg Lab Notebook -Due Monday, February 10th Title/Date

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  1. Hardy-Weinberg Lab Notebook -Due Monday, February 10th Title/Date Prelab (key concepts, materials, expected outcomes)  Key concepts: equations, 5 requirements for equilibrium, etc. 3) Purpose 4) Procedure, Hypotheses x3 (for each “case” that we complete,) Data (initial allele frequency, final genotypic COUNT, final allele frequency) for each case 5) ALL answers (#’d) for each case, all 6 H-W Problems (#’d)  You must write these answers in your lab notebook…do NOT staple lab packet into lab notebook! 6) Conclusion…brief but complete! Compare your hypothesis for each case to your results.

  2. Chapter 23: The Evolution of Populations • What is a population? • Localized group of individuals of the same species • What is a species? • Organisms that can mate & produce fertile offspring in nature • What is a gene pool? • All of the genes (both alleles) in a population at any time • What is a fixed allele? • An allele that is the same for all members of the population (rare) • How can we determine if a population is evolving? • Hardy-Weinberg Theorem….which actually describes non-evolving • populations….population is in equilibrium • Alleles & genotypes in a gene pool will remain constant unless acted on • by “outside agents” • p + q = 1 • p = dominant allele • q = recessive allele • 1 = ALL alleles in the gene pool

  3. Chapter 23: The Evolution of Populations • What is a population? • What is a species? • What is a gene pool? • What is a fixed allele? • How can we determine if a population is evolving? • Hardy-Weinberg Theorem….which actually describes non-evolving • populations….population is in equilibrium • Alleles & genotypes in a gene pool will remain constant unless acted on • by agents other than sexual recombination • p + q = 1 • p = dominant allele • q = recessive allele • 1 = ALL alleles in the gene pool • What if we want to know specific genotypes of individual in the population? • (p + q)(p + q) = 1 • p2 + 2pq + q2 = 1 • p2 = AA – homozygous dominant • q2 = aa – homozygous recessive • 2pq = Aa - heterozygotes

  4. Example p + q = 1 p2 + 2pq + q2 = 1 500 plants in a population A – pink flowers a – white flowers 20 white flowers (genotype = _____) How many pink flowers are there? _______ Given: 320 AA 160 Aa 20 aa How many flower color alleles in the population? ______ How many dominant (A) alleles? _____ How many recessive (a) alleles? _____ What is the frequency of the A allele? ________ a allele? ________ What is the genotypic frequency of AA flowers? ______ Aa flowers? ______ aa flowers? ______ aa 480 1000 = 500 x 2 800 = (320 x 2) + (160 x 1) 200 = (20 x 2) + (160 x 1) 0.8 = 800/1000 0.2 = 200/1000 0.64 = p2 = (0.8)2 0.32 = 2pq = 2(0.8)(0.2) 0.04 = q2 = (0.2)2

  5. Chapter 23: The Evolution of Populations • What is a population? • What is a species? • What is a gene pool? • What is a fixed allele? • How can we determine if a population is evolving? • What if we want to know specific genotypes of individual in the population? • What are the 5 requirements for a population to be in H-W equilibrium? • Large population • Isolated population • No mutations • Random mating • No natural selection • What happens if any one of these criteria is not met? • No more equilibrium & microevolution occurs • What are the causes of microevolution? • Genetic drift – gene pool changes of a small population due to chance

  6. CWCW CRCR CRCR CRCR CRCR CRCR CRCW CRCR CRCW Only 5 of 10 plants leave offspring Only 2 of 10 plants leave offspring CRCR CRCR CWCW CRCR CWCW CRCR CRCW CRCW CRCR CRCR CRCR CWCW CRCR CRCW CRCR CRCR CRCR CRCR CRCW CRCW CRCW Generation 2 p = 0.5 q = 0.5 Generation 3 p = 1.0 q = 0.0 Generation 1 p (frequency of CR) = 0.7 q (frequency of CW) = 0.3 Figure 23.7 Genetic drift

  7. Chapter 23: The Evolution of Populations • What is a population? • What is a species? • What is a gene pool? • What is a fixed allele? • How can we determine if a population is evolving? • What if we want to know specific genotypes of individual in the population? • What are the 5 requirements for a population to be in H-W equilibrium? • What happens if any one of these criteria is not met? • What are the causes of microevolution? • Genetic drift – gene pool changes of a small population due to chance • Bottleneck effect – a disaster reduces the population size so that the • surviving population is NOT representative of the original population • Founder effect – genetic drift in a new colony such as an island

  8. (a) Shaking just a few marbles through the narrow neck of a bottle is analogous to a drastic reduction in the size of a population after some environmental disaster. By chance, blue marbles are over-represented in the new population and gold marbles are absent. Bottlenecking event Surviving population Original population (b) Similarly, bottlenecking a population of organisms tends to reduce genetic variation, as in these northern elephant seals in California that were once hunted nearly to extinction. Figure 23.8 The bottleneck effect

  9. Founder effect: ~80% of the current members of the FLDS sect are descendants of just 2 men. Fumarase deficiency (a.k.a. “polygamist Down’s”) is prevalent.

  10. Chapter 23: The Evolution of Populations • What is a population? • What is a species? • What is a gene pool? • What is a fixed allele? • How can we determine if a population is evolving? • What is we want to know specific genotypes of individual in the population? • What are the 5 requirements for a population to be in H-W equilibrium? • What happens if any one of these criteria is not met? • What are the causes of microevolution? • Genetic drift – gene pool changes of a small population due to chance • Bottleneck effect – a disaster reduces the population size so that the • surviving population is NOT representative of the original population • Founder effect – genetic drift in a new colony such as an island • Gene flow – gain or loss of alleles due to immigration or emigration • Mutations – changes in an organism’s DNA can create new alleles • Non-random (selective) mating – favored alleles are selected for • Natural selection – variability within a population enables some organisms • to be better suited for survival and reproduction

  11. Chapter 23: The Evolution of Populations • What is a population? • What is a species? • What is a gene pool? • What is a fixed allele? • How can we determine if a population is evolving? • What is we want to know specific genotypes of individual in the population? • What are the 5 requirements for a population to be in H-W equilibrium? • What happens if any one of these criteria is not met? • What are the causes of microevolution? • What are polymorphisms? • 2 or more discrete traits within a population • ex. freckles, blood type • How can variation be preserved? • Diploidy – hides less favorable alleles in Aa until natural selection • favors them as aa • What is a heterozygote advantage? • Aa genotype has a selective advantage • Sickle-cell allele & malaria resistance

  12. Frequencies of the sickle-cell allele 0–2.5% 2.5–5.0% 5.0–7.5% 7.5–10.0% Distribution of malaria caused by Plasmodium falciparum (a protozoan) 10.0–12.5% >12.5% Figure 23.13 Mapping malaria and the sickle-cell allele

  13. Chapter 23: The Evolution of Populations • What is a population? • What is a species? • What is a gene pool? • What is a fixed allele? • How can we determine if a population is evolving? • What is we want to know specific genotypes of individual in the population? • What are the 5 requirements for a population to be in H-W equilibrium? • What happens if any one of these criteria is not met? • What are the causes of microevolution? • What are polymorphisms? • How can variation be preserved? • 12. What is a heterozygote advantage? • 13. How can natural selection change a population? • - Directional selection • - Disruptive selection • - Stabilizing selection

  14. Original population Frequency of individuals Phenotypes (fur color) Evolved population Original population (a) Directional selection shifts the overallmakeup of the population by favoringvariants at one extreme of thedistribution. In this case, darker mice arefavored because they live among darkrocks and a darker fur color conceals themfrom predators. (c) Stabilizing selection removesextreme variants from the populationand preserves intermediate types. Ifthe environment consists of rocks ofan intermediate color, both light anddark mice will be selected against. (b) Disruptive selection favors variantsat both ends of the distribution. Thesemice have colonized a patchy habitatmade up of light and dark rocks, with theresult that mice of an intermediate color areat a disadvantage. Figure 23.12 Modes of selection

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