Chapter 20 Variation and Selection in Populations 21-1
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Sectionsto study20.1 The Hardy-Weinberg law:Predictinggenetic variation in“ideal"populations20.2 What causes allele frequency to change in real populations?20.3 Ancestry and the evolution of modern humans21-2
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-2 Sections to study Sections to study 20.1 The Hardy 20.1 The Hardy-Weinberg law: Predicting genetic variation in Weinberg law: Predicting genetic variation in “ideal” populations populations 20.2 What causes allele frequenc 20.2 What causes allele frequency to change in real populations? y to change in real populations? 20.3 Ancestry and the evolution of modern humans 20.3 Ancestry and the evolution of modern humans
Prior to the 2Oth century, many people thought that “recessive"phenotypes such as naturally blonde or red hair would becomeextinct over timein human population.The blended inheritance theory claims thatthe information for blondeand red hair would be lost gradually when people with lighter hair colormated with peoplewith darkerhair.In1908,GeoffreyH.HardyandWilhelm Weinberg proposedthatif certain assumptions weremet, these phenotypes wouldremain constant overtime and between generations.21-3
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-3 Prior to the 20th century, many people thought that Prior to the 20th century, many people thought that “recessive recessive” phenotypes such as phenotypes such as naturally blonde naturally blonde or red hair red hair would become would become extinct over time in human population. extinct over time in human population. The blended inheritance theory claims that the information for b The blended inheritance theory claims that the information for blonde and red hair would be lost gradually when people with lighter ha and red hair would be lost gradually when people with lighter hair color ir color mated with people with darker hair. mated with people with darker hair. In 1908, Geoffrey H. Hardy and Wilhelm Weinberg proposed In 1908, Geoffrey H. Hardy and Wilhelm Weinberg proposed that if certain assumptions were met, these phenotypes would that if certain assumptions were met, these phenotypes would remain constant remain constant over time over time and between generations between generations
Population genetics: The scientific discipline that studies whathappens in wholepopulations at thegenetic level.Population geneticists rely on mathematical models in predicting apopulation's potential for stasis orchange.Simple models help clarifying the guestions about freguency of geneticdiseases orrate of spread ofpathogens,as well as making predictionsaboutfuturepopulations.21-4
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-4 Population genetics Population genetics: The scientific discipline that studies what : The scientific discipline that studies what happens in whole populations at the genetic level. happens in whole populations at the genetic level. Population geneticists rely on mathematical models in predicting Population geneticists rely on mathematical models in predicting a population population’s potential for stasis or change. s potential for stasis or change. Simple models help clarifying the questions about frequency of g Simple models help clarifying the questions about frequency of genetic diseases or rate of spread of pathogens, as well as making predi diseases or rate of spread of pathogens, as well as making predictions about future populations. about future populations
20.1 The Hardy-Weinberg law: Predicting geneticvariationin“ideal"populationsPopulation:A group ofinterbreeding individualsof the same species thatinhabit the same space atthe sametime.AlsocalledMendelian populationGirrafe herd on the African savanna21-5
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 21-5 Population Population: A group of : A group of interbreeding individuals interbreeding individuals of the same species that of the same species that inhabit the same space at inhabit the same space at the same time. Also called the same time. Also called Mendelian Mendelian population population. Girrafe herd on the African savanna 20.1 The Hardy-Weinberg law: Predicting genetic variation in “ideal” populations