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25 Cards in this Set
- Front
- Back
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Population genetics
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study of how populations change genetically over time
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What is population
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group of individuals in a particular place that are capable of interbreeding
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a locally interbreeding group within a geographic population may be called a
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subpopulation, deme or Mendelian population
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Gene pool
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sum total of genetic information present in a population at any given point in time
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genotype frequency
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the relative proportion of an allele at a particular gene locus
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allele frequency
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the relative proportion of an allele at a particular gene locus
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Hardy-Weinberg equilibrium
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-no mutation
-population is very large (no genetic drift) -mating combines gametes at random to form genotype (random mating) -there is no migration into or out of the population (no gene flow) -all genotypes survive and reproduce equally well (no selection |
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If Hardy-Weinberg is reached, total frequency is then
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1=p^2+2pq+q^2
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agents of evolutionary change
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-mutation
-genetic drift (small populations) -non-random mating -gene flow (migration) -selection (natural selection and sexual selection) |
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mutation
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ultimate source of genetic variation, has minor effect on allele frequencies
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two exceptions to mutation
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non-coding regions of DNA can evolve very rapidly dur to combination of relaxed selection and high mutation rate... mutation can rapidly generate genetic variation in bacteria and viruses (short generation times and horizontal gene transfer)
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Conjugation
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temporary joining of two bacterial cells and one-way transfer of DNA from donor to recipient
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Transformation
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take up of naked DNA from surrounding enviroment and incorporation of foreign DNA into host chromosome
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Transduction
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transfer of genes from one bacterium to another, with bacterial virus (bacteriophage) acting as carrier of the genes (vector)
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Mutation caused by transposable elements and horizontal gene transfer can be
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potent agent of evolutionary change in bacterial populations with important consequences for human health and disease
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genetic drift
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change in allele frequencies due to chance (stochastic)effects
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genetic drift (bottleneck effect)
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sudden change in enviroment may drastically reduce population size resulting in 1) change in allele frequencies 2)potential loss of alleles
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Genetic drift (founder effect)
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occurs when new population is started by few members of original population
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small population in founder effect
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reduced genetic variation compared to original population and disproportionate representation of rare alleles in founder population
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non-random mating
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changes genotype frequencies but not allele frequencies
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Inbreeding
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-mating between close relatives
-extent of inbreeding influenced by population size -exposes lethal recessive alleles and usually depresses fitness -mortality rate for children of first cousins higher than for offspring of unrelated parents -produces a deficit of heterozygotes and an excess of homozygotes |
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Assortative mating
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similar phenotypes mate preferentially with one another (blue-eyed person prefer one another as mates)
-increase homozygosity at some but not all loci |
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disassortative mating
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-dissimilar phenotypes mate preferentially (short with tall)
-increase heterozygosity -might be important at MHC loci |
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Gene flow (migration)
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movement of alleles from one population to another by:
-migration of fertile individuals -transport of gametes or immature stages (plants- transport by wind. marine species- transport by water currents) -mating of individual belonging to adjacent populations |
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benefits of gene flow
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restoration of alleles lost through genetic drift, and introduction of new beneficial alleles
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