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BIO342H5 (21)
Chapter 7


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Don Mc Kenzie

Chapter 7 Mendelian Genetics in Populations II Migration Genetic Drift and Nonrandom MatingPages 223228 232242 and 26427671 MigrationIt is the movement of alleles between populationsTo evolutionary biologists evolution refers to the gene flow the transfer of alleles from the gene pool of one population to the gene pool of another populationMechanisms behind this can vary from the occasional longdistance dispersal of juvenile animals to the transport of pollen seeds or spores by wind water or animalsThe actual amount of migration among populations in different species varies enormously depending on the mobility of individuals in the populationstresses placed on the populationAdding Migration to the HardyWeinberg Analysis Migration as a Mechanism of EvolutionTo explain this the text uses the oneisland model of migration found on page 225 figure 74oImagine two populations one on a continent and the other on a small island eg Africa and MadagascaroSince the island pop is small relative to the continent population migration from the mainland will be minor for allele and genotype frequencies on the continentoNow consider a single locus with two alleles A and A12Can migration from the continent to the island upset the HardyWeinberg equilibrium of the island YesAssume the frequency of A on the island is 10 Therefore the 1frequency of the A allele is 0 2When gametes in a gene pool combine at random to make zygotes the genotype frequencies for AA will be 1110 0 for A1A2 and 0 for AA22Also consider that there are 800 zygotes which will become adultsAssume that the continental population has a frequency of 10 for A and 0 for A opposite of the islands 21frequencies and consider that 200 individuals from the continent migrate to the islandNow there are 1000 individuals in total of which 80 is the original population A and 20 is the migratory 1population A2The A frequency is now 08 original was 10 and the A 12frequency is now 02 original was 10Thus the migration of the new population threw the HardyWeinberg Equilibrium out of balance on the islandEmpirical Research on Migration as a Mechanism of EvolutionRead the research on water snakes in Lake Erie on pages 227 and 228
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