Lecture 7 - vial = population size then the frequency of...

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Lecture 7 1) Crazy Bar Graph – Dr. Buri’s Experiment a) Frequency of heterozygous at the beginning is 100%. b) When a genetic population becomes fixed, there is no variance in an allele. c) Probability of fixation of an allele by genetic drift is determined by the frequency of that allele in a population (beginning of the experiment is 50/50, at the end of the experiment each allele is 50%) – Initial allele frequency correspond to probability of fixation. d) Genetic Drift decreases the genetic variation within a population, but among population, increases variability. e) Also an example of positive assortitive mating. f) By the end of the experiment (t + 18) some are fixed for bw75 allele and some are fixed for bw allele – populations polarized, and become more and more polarized with more generations. g) Genetic Drift is more significant on smaller populations – a small population would cause a quicker increase of fixed alleles within a population. h) (Started at 50% each) When you change the number of vials (not number of flies in the
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Unformatted text preview: vial = population size), then the frequency of the fixed allele would be less close to 50% at the end of the experiment. i) Each vial is like a coin toss – less vials, greater variance in fixing for bw allele or bw75 allele. ii) Genetic drift, not only adaptations, can cause differences among populations. iii) If started with not 50% each – easier to fix for bw75 2) Inbreeding Depression – Mating with relatives, offspring often suffer from reduced fitness. Can also happen if a single fly spawns a colony, t+1 is all inbreeding. i) Assortitive Mating – b) Mutations often cause loss of function (recessive) alleles, ie) deleterious recessives. c) Individuals homozygous for deleterious recessive alleles (because it is a diploid, this can happen) have reduced fitness. One copy of the deleterious “wild-type” recessive most likely won’t cause deleterious effects, but two together will....
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