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_Hardy Weinberg Lab.docx.pdf - Hardy-Weinberg Population...

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Hardy-Weinberg Population Genetics LabIntroductionIn the coming week, we will learnthat natural selection may beobserved in three patterns:stabilizing, directional, anddisruptive (or diversifying) selection.What circumstances might alterallelic frequencies in a population?To answer this, scientists oftenexamine the opposite question –under what circumstances wouldallelic frequencies in a population not change?In 1908 G.H. Hardy (an Englishmathematician) and W. Weinberg (a German physician) independently developed amathematical model that illustrates how, under specific circumstances, allelic frequencies ina population would remain constant.At that time, classical genetics was only beginning tobe explored while, at the same time, Darwin’s mechanism of evolutionary change was underscrutiny.Hardy and Weinberg proposed that changes in allelic frequencies would NOT occurif and only if the following conditions were met:(a)The population must be very large(b)No chance events occur that would reduce the population size (things such ashurricanes, tornadoes, tsunamis, etc.)(c)Mating within the population is random(d)There is no mutation(e)There is no immigration of individuals into the population or emigration from thepopulation(f)No one genotype is selected over anotherThe Hardy-Weinberg model provides anull hypothesisproposing that no evolution will occurif the normal influences of chance events, mutation, immigration and emigration, selectivepressures, population size, and non-random mating are removed from a population.The Hardy-Weinberg model provides a conceptual framework for later descriptions of thephenomena of gene flow and genetic drift that occur within populations.They assumedcorrectly that the evolutionary process was linked to changes in allelic frequencies at the
population level.By extrapolating and building up the ideas set forth by the Hardy-Weinbergmodel, evolutionary biologists were equipped to synthesize ideas about genes, organisms, andpopulations into an increasingly coherent explanation of the evolutionary process.By puttingtogether several previous hypotheses about biology and adding their own observations abouthow populations change, they built a robust model of evolution that is referred to as the“Modern Synthesis.”ProcedureIn this exercise, natural selection will be simulated by the selection of colored beads within aspecific environment. You will analyze the effects of selective pressures on a population thathas different color morphs, using the Hardy-Weinberg Equilibrium equation.

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Term
Fall
Professor
Baublitz

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