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Genomic screening for newborns
- Screening for large number of genetic diseases
- Better/earlier preventative treatement
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Genomic screening for personalized medicine
- Able to predict responses to different treatments and fine-tune drug therapy for individual
- Genetic testing of both patients and pathogens will allow faster and more precise diagnosis of many diseases
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What is population genetics?
The study of the genetic makeup of groups of individuals and how a group’s genetic composition changes with time
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What are Mendelian populations?
Groups of interbreeding sexually reproducing individuals that share the same gene pool.
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What is a gene pool?
A common set of genes in a population
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Population geneticists study:
- The variation in alleles within and between groups
- The evolutionary forces that shape patterns of genetic variation
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What causes phenotypic varation within a population?
Genotypic variation
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Genotypic frequency: f(AA)
f(AA) = (number of AA individuals)/N, where N is the number of individuals in the sample
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Calculating the frequency of an allele
freq of an allele = (# of copies of allele)/(# of copies of alleles at the locus)
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Allele frequency: p = f(A)
f(A) = (2nAA + nAa)/(2N)
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Calculate allelic frequencies from individual frequencies
p = f(A) = f(AA) + (1/2)f(Aa)
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Calculate allelic frequencies at loci with three alleles
p = f(A1) = (2nA1A1 + nA1A2 + nA1A3)/2N
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Calculate allelic frequencies from individual frequencies with three alleles
p = f(A1A1) + (1/2)f(A1A2) + (1/2)f(A1A3)
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Calculate allelic frequencies at X-linked loci
p = f(XA) = (2nXAXA + nXAXa + nXAY)/(2nfemales + nmales)
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Calculate allelic freq's at X-linked loci from individual frequencies
p = f(XA) = f(XAXA) + (1/2)f(XAXa) + f(XAY)
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Study example on slide 15
human MN blood-type antigens
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What assumptions does the Hardy-Weinberg law make?
The population is large, randomly mating, and not affected by mutation, migration, or natural selection
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The Hardy-Weinberg Law predictions:
- Prediction 1: The allelic frequencies of a population do not change
- Prediction 2: The genotypic frequencies stabilize (do not change) after one generation in the following proportions:
- p^2, 2pq, q^2
- The allelic frequencies determine the frequencies of genotypes
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If a population meets the Hardy-Weinberg assumptions, can it evolve?
Yes, but it requires external pressure.
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When a population is in Hardy-Weinberg equilibrium, the genotypic frequencies are determined by ...
the allelic frequencies
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