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Gene Frequency vs. Natural Selection
Team Married 2 The Game Courtney Bojorquez Devre Chavez Brittanya Jackson Daniel Santiago Corina Fontelera Jeff Flores James Luong Anna Martinez Chris Richard 2015 February
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What is Natural Selection and Gene Frequency?
The process theorized by Charles Darwin wherein organisms adapt to their environment over time and live to produce offspring. Weeds out the unfit individuals Selective towards traits best suited for environment Gene Frequency The ratio of a particular allele to the total of all other alleles of the same gene in a given population Also known as allele frequency
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Relationship Gene frequency gravitate to remain constant from generation to generation if the requirements for Hardy-Weinberg Equilibrium are met. Natural Selection is one of the factors that interferes with the equilibrium of gene frequency and the gene pool. However, Natural Selection enhances individuals that are well adjusted to the biological and physical conditions of their environment. Therefore, organisms with the best adaptations are more likely to survive, reproduce, and pass their successful alleles onto their offspring.
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Relationship cont... Unfavourable alleles Unfavourable alleles
Decrease (Green) Unfavourable alleles Increase (tan)
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Methods for Natural Selection
Natural Selection, a force in nature associated with evolution, was modeled. The key components for modeling this experiment involved using different colored dots to represent different specimens within a population, these different specimens were placed on different patterned maps to simulate them in different environments, student predators were introduced with different capabilities. Observed were several rounds of predation effects on several different specimens within a population in two different environments, while measuring specimen survival rate and growth rate of offspring to observe heritable traits for natural selection and natural selection resulting in adaption.
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Natural Selection Results
Light Blue species suffered one of the highest number of deaths in environment one. Least adapted for: Environment one (tied for most deaths, highest % of total deaths in env. 1: 65/35) Tiffany Blue suffered the highest number of deaths in environment two. new environment (67% of total env. 2 deaths) natural disasters (highest # of deaths) Similar colors experienced opposite results in both environments.
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Methods for Gene Frequency
Beads were use to represent species in a population. Two beads were randomly paired and their genotype is recorded. Gene frequency change, a mechanism associated with microevolution, was modeled Scenario 1 Place 50 Red Beads and 50 White Beads in a cup. Randomly pair to create RR homozygous dominant, Rw heterozygous, and ww homozygous recessive. 33% of ww homozygous recessive are selected against and place into death cup per gen in 5 generations Scenario 2 100% of ww homozygous recessive is selected against per each gen in 5 generations Scenario 3- Positive Mutation Use 40 Red, 40 White, and 20 Green Beads. Randomly sort pairs to create - RR Homozygous dominant, Rw Heterozygous, ww homozygous recessive, RB Heterozygous, wB Heterozygous, and BB homozygous. - 100% of ww is selected against, a positive mutation for 150% of RB Heterozygous, and 200% of BB. (Per each gen in five generations) Scenario 4- Negative Mutation Using 40 Red, 40 Green, and 20 Yellow Beads, randomly sort pairs to create -RR Homozygous dominant, Rw Heterozygous, ww homozygous recessive, RB Heterozygous, wB Heterozygous, and BB homozygous. - 100% of ww Homozygous recessive is selected against, 50% of RB Heterozygous is selected against, and 100% of BB homozygous is selected against. (Per each gen in five generations. Forecast data was calculated using slope equations from logarithmic trend lines for individual populations in each scenario. (see figures 6,7,8,9 in lab report)
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Gene Frequency Results
Negative Pressures: 0 % ww | GG 50% RG Neutral: RR | Rw | wG Heterozygous = Rw | wG Homozygous = RR | GG | ww Co-Dominant = RG When a Green allele is inherited with a Dominant allele it results in lower survivability. Allele Frequency at Gen 1 (Percent of total allele count) Frequency at Generation 6 Forecasted Freq. at Generation 12 Red 42% 78% 87% White 39% 19% 13% Green 3% 0%
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Comparison of GF to NS Organisms with negative pressures for green mutation that did not acquire any genetic variations to help adapt to their environment quickly perished. Organisms containing the green mutation allele became extinct by generation 10. In scenario 4, the green mutation is a perfect example of natural selection weeding out the unfit individuals and eliminating the non adapted population for better suited organisms in that environment.
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Comparison of GF to NS In Scenario 3, organisms which inherited allele frequencies of parent organisms due to positive selective pressures for the green mutation gene have a higher survival and reproductive rate that is best suited for their environment. Organisms adapted to their environment due to heritable biological traits survived and reproduced with inherited traits on the differential reproductive success of organisms interacting with their environment.
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Conclusion Natural Selection is a gradual process by which organisms with favorable traits tend to have a higher reproduction rate. Gene Frequency is conducive to remaining constant from generation to generation. Natural selection is easily reproducible in a laboratory setting; On the other hand, Hardy Weinberg is not easily reproduced in a lab setting due to restrictions on the population size. First Hypothesis: Disproved due to low population size and only six generations. Second Hypothesis: Since the co-dominant genotype went extinct (which is a form of natural selection), we disproved our second hypothesis. Third Hypothesis: This hypothesis was supported due to the small population size and survival rates (which inhibited Hardy Weinberg Equilibrium). Our data confirms that there is significant evidence in support of natural selection - however it is theoretically difficult to recreate an environment where the criteria for hardy-weinberg equilibria is attainable.
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References Reece, J., Wasserman, S., Urry, L., Minorsky, P., Cain, M., & Jackson, R. (2014). The Evolutionary History of Biological Diversity. In Campbell Biology (10th ed., pp ). Boston: Pearson. Huiming et al. (2014). Allele frequency changes due to hitchhiking in genomic selection programs. Genetics Selection Evolution, 46(1): 8. doi: /
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