Lecture_11 - I. Population Genetics A. Genotypic & Allelic...

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I. Population Genetics A. Genotypic & Allelic Frequencies B. Hardy-Weinberg C. Natural Selection Reading: Chapter 21 pg 757-768, Problems: 2-8, 18 Intro to population Genetics As I stated in my first lecture, the goal of this portion of the course is to start answering the question: what accounts for the variation among organisms that we observe – both variation among individuals of a species and variation among species. Of course what we're particularly interested in is the GENETIC basis of these differences and how they have arisen. Thus far, we've seen how Mendelian Genetics can describe the passage of traits through generations (pedigrees) - where given some information about the genetic nature of a trait you can predict the phenotypes and genotypes of future generations. Now we're going to move to a higher level, namely populations, to learn how we can describe the phenotypes and genotypes of populations of organisms and how these phenotypes and genotypes may change through time and space. POPULATION GENETICS First we need to describe the genetic variation within a population before we can describe how that might change. Two basic frequencies: Genotypic frequency Allelic frequency MN blood groups in humans: similar to the ABO blood groups - in that M & N alleles produce antigens on the surface of red blood cells In a sample of 1000 British people - were typed for MN blood groups: MM - 298 people MN - 489 NN - 213 1000
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In terms of GENOTYPIC FREQUENCIES: MM - 0.298 MN - 0.489 NN - 0.213 sum = 1.00 In terms of ALLELIC FREQUENCIES: 298 MM individuals have 596 M alleles 489 MN individuals have 489 M alleles 489 N alleles 213 NN individuals have 426 N alleles 1085 M alleles 915 N alleles (2000 total)
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This note was uploaded on 10/16/2010 for the course EEMB 129 taught by Professor Ajnarivera during the Spring '09 term at UCSB.

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Lecture_11 - I. Population Genetics A. Genotypic & Allelic...

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