Lec 4 Bild 3 2011 for TED

Lec 4 Bild 3 2011 for TED - Announcements -Discussion...

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Announcements -Discussion sections are in the rooms that are listed in the course catalog. TA office hours are listed in the syllabus and in the notes from the second lecture. -Interesting papers I emailed out are also available in our Bild 3 class section on TED under the Papers Related to Lectures section
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BILD 3 Lecture 4: The genetics of populations I. Basic probability (independent events) II. Hardy-Weinberg Equilibrium (p 2 + 2pq + q 2 = 1) III. Genetic Drift
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I. Probability How likely is it that something will happen? Probability – formal study of the laws of chance Probabilities are always between 0 and 1 . - combined chance of two independent events - chance of one OR another independent event
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1. Chance of two events happening: Chance of getting heads on a toss of penny = 1/2 Chance of getting heads on a toss of another penny = 1/2 Chance of tossing one penny AND another penny and getting heads on both tosses = 1/2 * 1/2 = 1/4 Combined chance of two independent events - multiplication problem
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2. Chance of one OR another event happening: Chance of getting 6 on one roll of die = 1/6 Chance of getting a 5 on one roll of a die = 1/6 Chance of getting a 6 OR a 5 on one roll is 1/6 + 1/6 = 2/6 = 1/3 Chance of one OR another independent event happening - addition problem
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BILD 3 Lecture 4: The genetics of populations I. Basic probability (independent events) II. Hardy-Weinberg Equilibrium (p 2 + 2pq + q 2 = 1) III. Genetic Drift
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II. Hardy-Weinberg Equilibrium Principle 1. If the allele frequencies are p and q , genotype frequencies will be p 2 , 2 pq , and q 2 2. The allele frequencies in a population will not change from generation to generation unless something changes them. G H Hardy 1877-1947 English mathematician Wilhelm Weinberg 1862-1937 German physician
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What would the genetic composition of a population be, if that population were NOT evolving? Why is this an interesting question? Null model – basis for comparison
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Definitions - review gene - the functional unit of heredity allele – alternative forms of a gene (A 1 or A 2 , A or a) locus (pl. loci) – location of a gene on a chromosome
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For now, we are concerned with a population … -of diploid and sexually reproducing organisms -with haploid gametes (egg & sperm) -with diploid zygotes (fertilized egg) -with two possible alleles at a locus (A 1 , A 2 ) And where, -homozygote = same 2 alleles at a locus (A 1 A 1 or A 2 A 2 ) -heterozygote = different alleles at a locus (A 1 A 2 )
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Imagine you have a population of alleles, sample at random to create zygote Allele frequencies used to calculate genotype frequencies: = 0.70 or 70% = A 1 = p (for HW) = 0.30 or 30% = A 2 = q (for HW) If a population is in Hardy-Weinberg equilibrium, then the frequency of alleles will not change from generation to generation
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Imagine you have a population of alleles, sample at random to create zygote Allele frequencies used to calculate genotype frequencies: = 0.70 or 70% = A 1 = p (for HW) = 0.30 or 30% = A
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This note was uploaded on 01/16/2012 for the course BILD 3 taught by Professor Wills during the Fall '07 term at UCSD.

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Lec 4 Bild 3 2011 for TED - Announcements -Discussion...

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