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41 Cards in this Set
- Front
- Back
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_______ biology’s central unifying concepts. It refers to the genetic changes in populations’ gene pools over time. |
evolution |
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__________ is a unit of evolution. It refers to all the individuals of one species that are present and interbreeding at a specific geographic location |
Population |
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Gene Pool |
-all gene copies in the population. -size of gene pool= 2xN (N= # individuals breeding) -can be described by genotype/ allelic frequencies |
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__________________ is a genetic trait w/ 2 or more distinct phenotypes. |
Polymorphism |
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___________ are proteins from different alleles |
Allozymes |
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What are ways of estimating genetic variation? (4) |
-visible phenotypic polymorphisms -choromosomal mutations -protein electrophoresis -DNA variation (sequencing) |
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Patterns of genetic variation can be explained by what? (5) |
-mate choice -mutation -dispersal (migration/ gene flow) -natural selection -genetic drift |
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The hardy-weinberg principle consists of (3)... |
-diploid, sexually reproducing species. It is assumed that every individual makes an infinite # of gametes -Gametes are randomly mixed in a “gamete pool”. -Gametes are randomly picked to form zygotes that represents the next generations, however, all adults die (Non-overlapping generations) |
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H-W Model Assumptions- HW equilibrium is ONLY found with (5)... |
-random mating -large population size (no genetic drift) -no mutation -no migration -no natural selection |
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How can you tell if a gene pool have H-W fre quencies? |
-Compare the expected genotype frequencies to observed w/ a chi-square goodness-of-fit test -If null hypothesis is rejected, the population doesn’t have H-W genotype frequencies. One of the 5 forces must be acting. |
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Matings based on phenotype/ genetic relatedenss |
Phenotype: -Positive Assortative Mating- mate w/ same phenotype more often (HoHe))negative> -Negative Assortative Mating- mate w/ same phenotype less often (Ho>He))negative>
Genetic Relatedness:)negative> -Outbreeding- mate w/ relatives less often (affects all genes; Ho>He))negative> -Inbreeding- mate w/ relatives more often (affects all genes; Ho
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Inbreeding Depression
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because inbreeding leads to increase chances of rare alleles being presented, then it leads to a decrease in survival/ reproduction |
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T/F: Mutation occurs at a higher rate than migration. |
False; Mutation is slow! |
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T/F: With the forward-backward mutation model, you will eventually reach equilibrium, despite which allele frequency you start off w/ (equilibrium= no net change of allele frequency; fixated). |
True! |
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Migration and Gene flow both bring in new alleles into a population. Their rates are much _______ than mutation rates. |
higher |
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What is known as the great homogenizer? |
Gene flow- alters freq. within populations, but reduces genetic dif. among populations |
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Is speciation retarted from gene flow? why? |
yes, because it requires genetic divergence (ability to be separated). genetic isolation is required to eliminate homogenizing effect of gene flow (need a barrier to prevent species from migrating into each other’s population). |
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One-Way Migration |
-example of this is wind blowing in one direction. Individuals from population 1 (due to factors such as wind) migrate into population 2. -After migration, allele frequencies in the source (population 1) are constant, while population 2 consists of proportion of ‘m’ migrants and ‘1-m’ of residents. -Eventually at equilibrium, the destination will reach the same as the source |
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Island Model Migration (migration is two-way) Assumptions.... (4) |
-ALL populations are discrete “islands” (no mainland) -ALL populations are equal in size, migration rate… but p and q don’t have to be the same in each population -The number of populations is large -Migration among “islands” is not distant dependent (migration rate m is constant over populations/ time) |
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__________ is due to random sampling error of gametes. |
Genetic Drift |
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______________ is the probability of a random event is only a theoretical expectation. Observed outcomes may differ from expected outcome; this has a larger impact on smaller populations. |
Random Sampling Error EX) flip a coin 10 times: you expect to get 5 heads/ 5 tails, but if you get 6 heads, then that’s a 20% deviation due to RSE. However, if you flip 1000 times, a 20% deviation (600 H/ 400 T) is very unlikely. |
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T/F: Fertilization is not subject to random sampling error |
False; it is
there are finite number of zygotes, which leads to RSE in gamete allele frequencies |
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T/F: Genetic Drift causes allele frequencies within a population to change over time (e.g. reach fixation) |
True! |
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T/F: THere is more GD in larger populations |
False; there is less GD in larger populations |
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Genetic drift causes population to ________ over time. |
Diverge |
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Effective Population Size |
-number of individuals able to breed |
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Genetic Drift causes ______ alleles to be lost easily. W/o variation, population eventually becomes __________. |
rare alleles; monomorphic |
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T/F: Genetic drift depends on Effective Population Size, not the actual # of individuals. |
True! |
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T/F: Genetic variation is lost slower when Effective Population Size is smaller |
False; lost faster |
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Bottleneck Effect |
reduction in population due to subpopulation being separated (i.e. form volcanoes, earthquakes, landslides etc.). A case of genetic drift. |
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Founder Effect |
new pop. initiated by small numbers of “founders”. Founders are only a SAMPLE of the source population. They are proned to Genet Drift, and lose variation. A case of genetic drift. |
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Natural Selection |
-increase in the freq of beneficial alleles over time due to inc survival and reproductive success of ind. carrying those alleles -Other Forces Involved: Even if NS selects for/ against an allele, other ev. forces will impact the selection of that allele. |
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T/F: Natural selection operate on genotypes, causing populations to better ADAPt to their environment. |
False; operates on phenotypes |
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_______________ refers to the capacity to survive/ reproduce based on phenotypic dif. among ind. |
Fitness |
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What are the 4 different types of selection? |
-Gametic Selection- some genes in gametes more compatible than others -Viability Selection- avg. % survival -Sexual Selection- mating -Fertility Selection- avg. # offspring per surviving adult |
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What are the 4 types of natural selection? |
-complete dominance- selection against recessive allele -partial dominance -overdominance- selection against homozyogote -underdominance- selection against heterozygote |
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complete domoninance |
-selection against recessive allele
-A2 can be fixed if there were no A1 alleles initially -The rate of fixation of the recessive alleles decrease after each generation because the rec. found most freq. in heterozygotes |
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Partial Dominance |
for s>0 and p>0, population becomes fixed for A1 (stable)for p=0, population remains fixed for A2 (unstable) |
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Underdominance |
- selection against heterozygote/ heterozygotes have lowest fitness -population becomes fixed for A1 or A2= stable equilibrium. But if both alleles exist in the population, there’s unstable equilibrium. -If p=.5 & q=.5, then i’s unstable equilibrium |
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Overdominance |
-selection against both homozygotes (S11/ S22 don’t have to be the same) -Two unstable equilibrium (fixed for A1 or A2) -THE ONLY NS THAT MAINTAINS POLYMORPHISM/ THE MOST DIVERSITY! -rare in nature/ not plausible |
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What's the only natural selection that maintains polymorphism? |
overdominance- against homozygotes |
