MidTerm2_PartA_Handout.2009

MidTerm2_PartA_Handout.2009 - BIS 2B WINTER 2009 POPULATION...

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BIS 2B WINTER 2009 POPULATION GENETICS ___________________________________________________________________________________ __ ___________________________________________________________________________________ __     I.  T OWARD   A  G ENETIC  D EFINITION   OF  E VOLUTION a) The loss of variation by … 1) blending inheritance. 2) selection. b) The generation of variation by … 1) mutation (new cards added to the deck). 2) sexual reproduction (the deck gets reshuffled each generation). 2.   Transmission genetics  (rules governing transmission of gene from parent   offspring). 3.   Population genetics  (rules governing changes in gene frequencies in populations) 4.   Microevolution  (evolutionary change within a breeding unit or species)  versus  Macroevolution  (evolutionary   change at and above the species level). 5.   Phenotypic   versus   genetic  definitions of microevolution: the importance of heritable/genetic  (rather than phenotypic) changes. a) Why we care about genetic changes 1) Dominance 2) Epistasis 3) Environmental effects: norm of reaction b) But remember, NATURAL SELECTION USUALLY ACTS ON PHENOTYPES, NOT  GENOTYPES 6.   A GENETIC DEFINITION OF EVOLUTION :     CHANGE   OVER   TIME   IN   THE   PROPORTIONS   OF   INDIVIDUAL   ORGANISMS   DIFFERING   GENETICALLY   IN   ONE   OR       MORE   TRAITS     .     Such changes transpire by…  the origin and subsequent alteration of the frequencies of alleles or  genotypes from generation to generation within populations [ MICROEVOLUTION ];    the alteration of the proportions of genetically differentiated populations of a  species; or by changes in the numbers of species with different characteristics  [ MACROEVOLUTION ].  
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BIS 2B, Winter 2009 Page  2 II.  M ENDELIAN  G ENETICS   TO  P OPULATION  G ENETICS a)  Individual  organisms do NOT evolve: their genetic composition cannot change. 1) Individuals have genotypes, but offspring never have the same genotypes as  their parents (unless they are cloned).  The genotype is destroyed when an organism dies.  Offspring usually get their genes from two separate parents b)  Population : all the diploid individuals that  actually   interbreed  ( i.e ., exchange genes) 1) Comparisons of relative reproductive success/fitness: fruit flies  vs . humans. c) 
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This note was uploaded on 10/08/2009 for the course BIS 2 taught by Professor Schwartzandkeen during the Spring '09 term at UC Davis.

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MidTerm2_PartA_Handout.2009 - BIS 2B WINTER 2009 POPULATION...

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