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Population GeneticsGenetic VariationGenetic variation is a measure of the variation that exist in the genetic makeup ofindividuals withinPopulation.Genetic VariationGenetic variation is a measure of the genetic differences that exist within a population.The genetic variation of an entire species is often called genetic diversity. Geneticvariations are the differences in DNA segments or genes between individuals and eachvariation of a gene is called anallele. For example, a population with many differentalleles at a single chromosome locus has a high amount of genetic variation.Geneticvariation is essential for natural selection because natural selection can only increaseor decrease frequency of alleles that already exist in the population.Genetic variation is caused by:MutationRandom mating betweenorganisms random fertilizationCrossing over (or recombination) between chromatids of homologouschromosomes during meiosisThe last three of these factors reshuffle alleles within a population, giving offspringcombinations which differ from their parents and from others.AdAdPopulation Genetics | Boundless Biology[9/16/2020 2:14:48 PM]
Evolution and Adaptation to the EnvironmentVariation allows some individuals within a population to adapt to the changingenvironment. Because natural selection acts directly only on phenotypes, more geneticvariation within a population usually enables more phenotypic variation. Some new allelesincrease an organism’s ability to survive and reproduce, which then ensures the survivalof the allele in the population. Other new alleles may be immediately detrimental (such asa malformed oxygen-carrying protein) and organisms carrying these new mutations willdie out. Neutral alleles are neither selected for nor against and usually remain in thepopulation. Genetic variation is advantageous because it enables some individuals and,therefore, a population, to survive despite a changing environment.Genetic variation in the shells of Donax variabilis: An enormous amount of phenotypicvariation exiss in the shells of Donax varabilis, otherwise known as the coquina mollusc.

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