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Population Genetics - Micro and Macroevolution and Taxonomy

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Anthropology 1026F/G
Andrew Nelson

Jan 24 12 Population GeneticsMicro and Macroevolution and TaxonomyGenome size does not correlate with evolutionary status nor is the number of genes proportionate with genome size Humans have around 25 000 and we are heterozygous at about 6 of those loci this makes our general make up the same 1500Therefore we are capable of producing 2 different possible combinations of those genes and this leads to lots of combination this causes our differences Gene locus is a address for a particular gene but the gene does not tell you what the DNA is Alleles are specific contents of genesPopulation Genetics A population is a community of individuals of a sexually reproducing species within which matings occur They pass those genes along from one generation to the next Population is the unit of evolution and the individual is the unit of selection lives or dies and this determines what they pass onEvolutionChange of Allele Frequencies Over Time Evolution is defined as change in organisms over time but this is not very preciseIt is the population that changes over time and an individual does not evolve You describe a population by looking at the central tendency the mean through variability range standard deviation variance and the frequency of the occurrence of particular traits or genes If half of the genes in a population of pea pods code for the trait smooth and smooth is a dominant trait the frequency of S05 therefore the frequency of the trait wrinkled which is recessive smooth is frequency 05 We now say evolution is a change in allele frequencies over time in a population With time small changes can accumulate to be big onesFactors that Change Allele Frequencies Mutation affects allele frequencies and is the ultimate source of new traits frequency goes from 0 to something Natural selection or the editor reduces variation and reduces the frequency of maladaptive traits and therefore increases the frequency of adaptive traitsMigration is the movement of individuals and their alleles into and out of populations and this can change the frequency of occurrence of alleles could take away good or bad traits so it can be a good of bad thing for the original population Nonrandom mating changes the frequency of the traits being focused on thus increasing this trait or reducing others Genetic drift causes changes in allele frequency due to random factors that affect presence survival or mating of individuals within a populationExample is Tristan de Cunha where in 1817 a British garrison placed watch over Napoleon and a few men stayed and advertised for wives and they came and a few others By 1885 60 of the genes could in the population be traced to the two men and their wives By 1960 there were 260 people on the island and 1 had retinitis pigementosa and this was a rare trait with a frequency world wide of 0025 Greatly increased frequency due to random factors caused this jump in numbers and there were greater effects because the population was smaller HardyWeinberg Model of Genetic Equilibrium First formulated to explain why dominant alleles dont swamp recessive ones Hardy was a mathematician and not familiar with biology but he had people who were with genetics around him and they could not figure out why allele changes were occurring Hardy looked at their math and he said it was just the way the system worked and said it was a problem of frequency of equilibrium
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