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 wont cause deleterious effects, but two together will....
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