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14 Cards in this Set
- Front
- Back
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What is fixation? |
Losing all alleles except one in the preceding generation. So "fixed" the allele that is left. (small populations drift very quickly and lead to fixation, while large populations drift very slowly) (As long as population is changing randomly genetic drift is happening, if it is not random then it is natural selection where the environment causes evolution) |
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Define a population |
A group of (potentially) interbreeding individuals of a particularspecies. (w/ some reproductive isolation from other populations) |
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What are SNPs? |
Single Nucleotide Polymorphisms (SNPs), where only one nucleotide varies (usually between just 2 bases/alleles) Indel = where an insertion or a deletion of bases occurred Microsatellite = a region where short sequences (e.g. AG) are repeated, and the # of repeats varies between individuals |
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What is pharmacogenomics? |
Tailoring medical treatments to fit an individuals genotype |
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How do you calculate for p and q? |
Ex. Observed600 red-flowered plants, 300 pink-flowered plants, and 100 white-flowered plants: [# homozygotes + (1⁄2 x # heterozygotes)] / (total # individuals) p = [600 + (0.5 x 300)] / 1000 = 0.75 q=[100+(0.5x300)]/1000=0.25 |
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What hypothesis are you accepting when there is a HWE? |
When there is a Hardy Weinberg Equilibrium, we assume that ournull hypothesis is true, and that the population is NOT evolving. |
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How do we calculate the probability of getting a particular genotype? |
By multiplying appropriate probabilities together. - If the population is not evolving, p and q should stay constant. - If the population is mating randomly, you can imagine that each offspring is made by randomly drawing 2 alleles from the gene pool (and the probability of getting CR = p, and P(CW) = q). |
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How do we calculate the expected # of (for ex.) plants with each genotype? |
Expected # of CRCR = p2 x total number of observed plants = (0.75)2 x 1000 plants observed in total = 562.5 red plants expected. Because p2 = Probability of getting CRCR = The expected proportion of the populationis CRCR, when the population is at HWE. (Therefore, to convert a proportion to a #, multiply by the total #) Expected # of CWCW = q2 x total number of observed plants Expected # of CRCW = 2pq x total number of observed plants |
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Assuming the population is at HWE, how do we know if the population is evolving? |
We do a chi-squared test to find out for sure. X2 for CRCR = (600-562.5)2 / 562.5 = 2.5 X2 for CRCW = (300-375)2 / 375 = 15 X2 for CWCW = (100-62.5)2 / 62.5 = 22.5 TotalX2 =2.5+15+22.5=40 df = 2-1= 1, and so p<0.005 **more than 99.5% sure that this population is not at HWE,and it is therefore evolving |
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What is one type of non-random mating? |
Assortative mating: When individuals with similar genotypes/phenotypes (for a particular trait) are more likely to interbreed. |
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What is the second type of non-random mating? |
Inbreeding: when mating between genetically-related individuals occurs more often than expected, based on random mating. Negative inbreeding: when mating between genetically-relatedindividuals is happening less often than expected, based onrandom mating. **For inbreeding & assortative mating,genotypic frequencies change (fewerheterozygotes), but allele freq.does NOT change. Meansno evolution is occurring,(even though thepopulation is not at HWE) |
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What are three mechanisms that can cause evolution? |
1) Mutations: can create new alleles 2) Migration: can introduce new alleles and/or change allele frequencies 3) Natural Selection: decreases the frequency ofdeleterious alleles, and increases the frequency of alleles thatincrease evolutionary fitness. |
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There are two types of mutations: |
Silent mutations: stay rare, or are lost due to genetic drift. Deleterious mutations: are lost even faster (natural selection) **Mutations are important because natural selection acts onvariation, and mutations are the key sources of new alleles. |
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How do you calculate the frequency of an allele after a migration? |
A population of 900 lake trout with afrequency of p = 0.6 for allele A. Flood transfers 100 trout from aneighboring lake, which has an allele frequency of p = 0.2. Whatis the freq. of allele A in your lake, after this migration event? m= migration rate or proportion of individuals that are immigrants = # of new trout introduced / total # trout in lake after migration = 100/1000 = 0.1 p = allele A frequency in original population = 0.6P = allele A frequency among the newly introduced trout = 0.2 p new= (1-m)p + mP = (0.9)(0.6) + (0.1)(0.2) = 0.56 |
