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61 Cards in this Set
- Front
- Back
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What are the five measures of microevolution? |
1) DNA sequences 2) Allele frequencies 3) Polymorphic/monomorphic genes 4) Allele diversity 5) Average heterozygosity |
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What is Allele (Haplotype) frequencies? |
-A form of determining the frequency of alleles -Heterozygosity is when two alleles are different -Homozygosity is when two alleles are the same |
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What is a polymorphic/monomorphic gene? |
-A gene is polymorphic if the frequency of the most common allele is less than a given percentage -A monomorphic gene has only one allele |
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What is allele diversity? |
-This can be found by figuring out the percentage of heterozygosity in a specific loci in a population.
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What are the four evolutionary forces affecting allele frequencies? |
1) Natural selection 2) Mutation 3) Gene Flow 4) Genetic Drift |
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What is natural selection? |
-Natural selection can be seen in various forms: Stablising selection, directional selection, diversifying selection, sexual selection. -The more ´fit´ an organism is, the more likely it will have offspring that will also bread. -Fitness is a relative measure of genotypes against other genotypes. -Fitness may change if the environment changes. |
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What is mutation? |
-Mutation is the ultimate flow of genetic variation. -Evolutionary rates are typically low if mutation rate is also low -Mutation can be beneficial and deleterious |
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What is gene flow/migration? |
-Migration refers to the movement of individuals in/out of a population -Not all types of migration (ie seasonal) result in exchange of genes -Gene flow refers to number of migrants that have contributed in exchanging genetic information. |
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What is genetic drift? |
-Chance fluctuations in allele frequency which occur in finite populations -Bigger impact in smaller population -After a sufficient number of populations, alleles either become fixed or lost, and genetic diversity decreases. |
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What is effective population size? |
-Effective population size is usually much lower than actual population size -Effective population size are the individuals who contribute genetically. |
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What are the three instances that directly influence effective population size? |
1) Variable population number 2) Unequal sex ratios 3) Uniform population dispersion |
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What is a bottleneck? |
-When an event causes a population to descend to a small number of individuals. -This can lead to loss of genetic diversity. -Populations that bottleneck may lose some alleles present in previous generations. |
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What do the symbols k, Ne, P and μ mean? |
k = rate of evolution Ne = No. of individuals carrying an allele μ = how quickly alleles are generated P = how quickly alleles are fixed k = NeμP |
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What is the neutrality hypothesis? |
-On the molecular level, rate of evolution is determined by the rate of mutation/random drift. k=μ -This lets us find rate of mutations in the past. |
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What is a population model? |
-A discrete population model is most commonly used. -All individuals are potential partners (random mating) -Each subpopulation is connected to other subpopulations |
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How does gene flow (immigration) effect genetic diversity in a population? |
-The more gene flow between subpopulations means a higher genetic diversity. -Lower gene flow equals less genetic diversity |
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What is the Fst Statistic? |
-Theoretical value of Fst ranges from 1 to 0 -Assumes random mating -Hs: average expected subpop heterozygosity -Ht: average expected totalpop heterozygosity Fst = (Ht - Hs)/Ht -If subpop and totalpop have same heterozygosity, then total heterogeneity is the same value Hs = Ht. -If there is no heterozygosity, Fst = 0 |
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What does it mean 0 < Fst < 1 mean in a population. |
-This means that the subop heterozygosity and totalpop homozygosity. -High gene flow often results with Hs = Ht -Low gene flow often results with Hs = 1 |
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Subpop1: p=0.55 q=0.45 Subpop2: p=0.55 q=0.45 Subpop3: p=0.55 q=0.45 What is the average expected subpopulation heterozygosity? H = 2xpxq |
Subpop1: p=0.55 q=0.45 Subpop2: p=0.55 q=0.45 Subpop3: p=0.55 q=0.45 Hs = heterozygosity in subpops Hs = (2x0.55x0.45 + 2x0.55x0.45 + 2x0.55x0.45)/3 Hs = 1.485/3 Hs = 0.495 = 49.5% |
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Subpop1: p=0.55 q=0.45 Subpop2: p=0.55 q=0.45 Subpop3: p=0.55 q=0.45 What is the average expected total population allele frequency? |
Subpop1: p=0.55 q=0.45 Subpop2: p=0.55 q=0.45 Subpop3: p=0.55 q=0.45 p = (0.55 + 0.55 + 0.55)/3 = 0.55 q = 1-p = (1 - 0.55) = 0.45 Ht = 2xpxq = (2x0.55x0.45) = 0.495 |
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If Ht = 0.495, and Hs = 0.495, what is the Fst? |
Fst = (Ht - Hs)/Ht = (0.495 - 0.495)/0.0495 Fst = 0 (high gene flow) |
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What is conservation genetics? |
The application of genetics to preserve genetic variation within a species, capable of coping with genetic change. |
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What are three important aspects of genetic diversity? |
1) Genetic management of small populations 2) Understanding species' taxonomy/biology/ecology 3) Molecular markers for forensics |
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What is the concern for conservation genetics? |
-Genetic factors that affect extinction risk -Genetic management that attempts to minimise this risk -Identification of genetic diversity -Management of diversity in captive populations |
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What are some extinction factors a species may face with low genetic variability? |
-Inbreeding and loss of genetic diversity in small pops -Reduced fitness - lower production/survival rates -Diminished capacity to evolve in response to environmental change -Effects of inbreeding/loss of genetic diversity can interest and create an ¨extinction vortex¨ (Small pop>Inbreeding>reduced adaptability>Reduced N>small pop) |
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What is genetic load - purging? |
The accumulation and loss (purging) of deleterious mutations |
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What is inbreeding depression? |
-The deleterious effects of inbreeding on reproduction and survival -Reduced survival |
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What is population fragmentation? |
-Reduced gene flow and changes in gene flow within a structured population. |
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Why is resolving taxonomic uncertainties important? |
-It is important to determine relationships of species, and species status (ie discovering that one species is actually two similar species) |
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What are important biological/ecological characteristics? |
Use of genetic analysis to understand aspects of a species biology/ecology that may not be available any other way. |
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What is a loss-of-function mutation? |
-A gene can be knocked out by base pair substitutions that produce a chain terminating codon. |
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Why can´t natural selection remove a lethal recessive mutation from a population? |
-Natural selection only works on phenotypes - not genotypes -A lethal recessive gene can not be removed because it can still exist in the heterozygous state -it ´hides´ behind the dominant allele, and natural selection cannot remove it. |
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What is directional selection? |
Directional selection changes the means of a population over time (shifts up or down the X axis (left/right)) |
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What is disruptive selection? |
-Not overly common -Individuals with extreme phenotypes have advantage -Bell curve dips in the middle, higher at ends -ie birds with strong or small beaks have advantage over birds with average beaks |
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What is stablising selection? |
-Individuals with extreme phenotypes are at disadvantage -Ends of bell curves are in ´critical region´ and natural selection removes them -This makes bell curve thinner |
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Why does natural selection deplete and maintain genetic variation? |
-Lethal alleles lower in frequency over time -Beneficial alleles raise in frequency over time -At any given time, both lethal and beneficial alleles equal up to 1. |
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What does it mean when alleles reach a stable equilibrium? |
-Stable frequency means two alleles on a graph will always end up with the same frequency over time. -This is typically around halfway (0.5) |
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What does an unstable equilibrium mean? |
Unstable equilibrium means that alleles will eventually reach a 1 or 0 frequency rate. |
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What does genetic death mean? |
Genetic death means natural selection will eventually kill you due to alleles you possess. |
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Why do species maintain variation instead of becoming fixed in only beneficial alleles? |
Species maintain variation because a particular variation in the genome may be useful in the future. |
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What are MHCs? |
-MHCs are molecules which embed in macrophages (large, white blood cells that inject foreign substances) -MHCs allow our immune system to identify viral/bacterial invasion. -Increasing variation on genetic variation underlying MHCs will reduce extinction factors. -Low MHC variation = low survival rate |
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On what scale does microevolution operate? |
Microevolution refers to the changes within a species or a population. |
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On what scale does macroevolution operate? |
Macroevolution happens on the scale of seperated gene pools. |
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What restrains the process of natural selection? |
-Natural selection is restrained to the past. It can only work on inherited variation. It can not create more variation. -Natural selection can only work on an organisms phenotype. It can only indirectly effect the genotype. |
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Can an individual organism evolve? |
No, populations and species can evolve. Not single organisms. |
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If 46% of a species gene pool is heterozygous, what is the percent of homozygosity? |
-If 46% of a gene pool is heterozygous, then 54% is homozygous. -A gene pool can only be homozygous or heterozygous. |
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Under what conditions should completely prevent the occurrence of natural selection? |
-When a population can live in a habitat with no competing species. (double check) |
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Are the present use of an animals features the reason they were evolved? |
No. Although birds use feathers for flight, it is predicted that the feathers initial use was to keep birds warm. |
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What variable is likely to undergo the largest change when a new allele is added to a loci that was formerly fixed? |
The biggest change will be the percentage of average heterozygosity. |
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What is the smallest unit upon which natural selection can direly effect? |
-An individuals phenotype -Natural selection cannot select for genotypes |
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What is the smallest unit that natural selection can change? |
-A populations gene frequency -Done so indirectly by selecting for beneficial phenotypes |
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What process is more likely to influence gene frequencies in small populations than larger ones? |
Genetic drift |
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The higher the proportion of loci that are fixed in the population, the lower the (2): |
-Nucleotide variability -Average heterozygosity |
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What is the estimated frequency of the dominant allele A in a gene pool? |
-Around 50% |
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What proportion of a population is probably heterozygous (Aa)? |
q = 0.5 p = 0.5 2pq = 2x0.5x0.5 0.25 -> 25% |
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Allele´s A and a are at equilibrium, with a frequency of 0.1, what is the percentage of heterozygotes? |
p = 0.1 q = 0.1 2pq = 2x0.1x0.1 =18% |
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In a population of 1000, 480 have alleles AB, and 360 have BB alleles. What is the frequency of the B allele? |
AB = 480/2 = 240 BB = 360 B total = 600 Proportion: 600/1000 = 0.6 60% of the population have the B allele. |
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Gene flow is a concept best used to describe an exchange between: |
Populations |
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Darwinian fitness of an individual is measured by: |
The number of an organisms offspring that survive to reproduce |
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If neutral variation is truly neutral, then it should have no effect on: |
If neutral variation is neutral, then it should have no effect on relative fitness |
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What is the heterozgygote advantage closely related to: |
Stabilising selection. |
