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Dominance (genetics) wikipedia , lookup
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HardyWeinberg Equilibrium WHAT HAPPENS IF IT DOESN’T Hardy -Weinberg Under certain conditions the frequency of an allele will remain the same Hardy -Weinberg No Mutation No immigration or emigration Large population No Natural Selection Random Mating Hardy -Weinberg Use p & q to represent allele frequency p (%) + q (%) = 1.00 (100%) P2 +2pq + q2 = 1.00 (100%) Disruptions to Equilibrium Mutations Could produce new alleles (spontaneous) Hard If to eliminate harmful recessives helpful become part of population Disruptions to Equilibrium Migration Emigration – exit Immigration – into Disruptions to Equilibrium Genetic drift Allele frequencies change Happens in small population Leads to no variation & possible extinction Disruptions to Equilibrium Non random mating Geographic proximity Many species have mate selection Disruptions to Equilibrium Natural selection stabilizing – selects for the average directional – selects for extreme disruptive–selects sexual for either end – choose mates Concepts of species morphological based on looks - what look like 2 different species can breed & produce fertile off spring Concepts of species biological – populations of organisms that can breed & produce fertile offspring, but do not breed with other groups Concepts of species Modern – single type of organism that are morphologically similar, can interbreed & produce fertile offspring Types of speciation Allopatric speciation Results because a physical barrier is present Types of speciation Sympatric Speciation Results when there are no barriers, from natural selection, mutation and genetic drift Isolation Mechanism 1. geographic – physical separation (island & rivers) 2. Reproductive – unsuccessful breeding Reproductive isolation Post- zygotic – after fertilize offspring can’t reproduce Ex: mule, seedless grape Reproductive isolation Pre – zygotic before fertilize Ex: mating times Rates of Speciation gradual – slow shift in the forms that are seen punctuated – sudden shift in the forms seen in the fossil record