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16 Cards in this Set
- Front
- Back
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Deme
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- Structure of a population into several more or less sub populations
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Variance
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- Variance = (p0)(q0)/2N - dispersion of allelic frequencies around the average value (considered drift)
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Standard Deviation
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- s = sqrt*(p0q0/2N). - Variance in all relic frequency increases at a slower rate as the number of generations increases
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Genetic Drift
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- How allelic frequencies change as a result of sampling error
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Effective Population Size
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- Size and structure of breeding portion of a population. - Less than total population. - Factors that influence: unequal numbers of male and females (N = (4m*f)/(m*f)), unequal numbers of successive generations (N = 1/((1/t)(1/N1 +•••))).
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Founder Effect
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- When a pop is founded by a small number of colonists they will not carry a perfect sample of alleles from parent pop and will lose genetic variation compared to parental pop. - Enhanced by genetic drift - Ex: Ellis-van Creveld Syndrome in Amish
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Genetic Bottleneck
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- Population goes from a relatively large size with large genetic variation, down to small size with relatively small amounts if genetic variation, back up to a larger size but with similar low genetic variation of the smaller population size
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Inbreeding
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- Mating between relatives - Ancestors calculated by 2^t. - smaller the pop, more recent common ancestors. - Increase in homozygotes, but no change in allelic frequency
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Coefficient of Inbreeding (F)
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- Probability that the two alleles at a single locus are related by descent. - F = (2pq - H) / 2pq
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Autozygous
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- Two alleles at any locus that originate from the replication of the same strand of DNA in a previous generation. - Identical by descent
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Allozygous
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- Two alleles at any locus that do not originate from the replication of the same strand of DNA in a previous generation. - Independent of descent
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Assumptions of Idealized Populations
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- Constant Size. - Randomly Breeding - No mutation. - No migration. - No Selection. - No Overlapping Generations
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Genetic Drift in Ideal Populations
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- Allelic freq. fluctuates at random independently of one another in different pops or demes (also true for alleles at different loci if the genes are not linked). - Different populations or demes diverge in allelic frequencies - After enough time, a single allele will become fixed at each gene locus. (Probability that allele will become fixed equals the frequency of that allele. - Ultimate reduction of genetic variation within a pop or deme. - Rate of these events is inversely related to pop size
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Genetic Bottlenecks Ex
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- Northern Elephant Seal populations. - population was reduced significantly and after growing the pop still does not have genetic variation
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Genetic Drift and Mutation, Migration, and Selection Ex
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- Mutation rate for locus (N = 1/X) effective pop size needed to counteract genetic drift
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Fruit Flies: Genetic Drift Brown Eye Color Experiment
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- 107 populations of 8 males and 8 females heterozygous for 2 alleles with initial freq. of .5 bred through 19 generations. - Freq. Varied among populations but overall average remained around .5. - Increase in homozygotes and decrease in heterozygotes. - Allelic freq in individual pop across generations diverged more from initial freq
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