1 weak forces in evolution dan graur. 2 changes in allele frequencies are important. changes in...
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Changes in allele fr
equencies are
Changes in allele fr
equencies are
importantimportant..
Changes in genotype
frequencies are
Changes in genotype
frequencies are not not
so importantso important..
1.1.
2.2.
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Deviation from randomness:Deviation from randomness:By genetic similarity:By genetic similarity:
Assortative matingAssortative matingDisassortative matingDisassortative mating
By genetic relatedness:By genetic relatedness:InbreedingInbreedingOutbreedingOutbreeding
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Strong assortative mating by skin color in the US
Percentage of non-hispanic whites: 80%Percentage of blacks: 13%Expected percentage of interracial marriages: 10.4%Observed percentage of interracial marriages: 0.9%
Ratio of = 2:1
white female/black male black female/white male
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Assortative mating Assortative mating is very strong in is very strong in humans even with humans even with respect to respect to non-non-geneticgenetic traits. traits.
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Inbreeding is Inbreeding is usually usually forbidden… forbidden…
An exception!An exception!
C vii
P xii C v
P ix
P = PtolemyC = Cleopatra
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The fishThe fish Rivulus Rivulus marmoratusmarmoratus exhibits the exhibits the most extreme form of most extreme form of inbreeding: inbreeding: SelfingSelfing
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Even if extreme extreme deviations deviations from random from random matingmating occur in all generations, allele allele frequencies frequencies remain remain constantconstant.
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Mating pattern Mating pattern is is notnot an important an important
evolutionary force evolutionary force
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However, because of gene flow, the two subpopulations are, in fact, one population, in which allele frequencies do no change.
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Mutations are the Mutations are the ultimate source of ultimate source of variation. Only variation. Only mutations can mutations can create gcreate genetic enetic novelnovelty. ty.
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Mutations arise all Mutations arise all the time. Per the time. Per definition, the definition, the initial frequency initial frequency of a mutation in a of a mutation in a diploid population diploid population is 1/2N.is 1/2N.****N = population sizeN = population size
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The human population on The human population on October 31, 2011 was October 31, 2011 was estimated to be 7 billion estimated to be 7 billion people. The number of people. The number of alleles at an autosomal alleles at an autosomal locus is, therefore, 14 locus is, therefore, 14 billion. A mutation arising billion. A mutation arising today in the human today in the human population will have an population will have an initial frequency of about 7 initial frequency of about 7 × 10× 101111……
……resulting in a change in resulting in a change in allele frequencies fromallele frequencies from 00 toto 0.00000000007.0.00000000007.
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Mutation is the Mutation is the ultimate source of ultimate source of variability, but it is variability, but it is notnot an important an important evolutionary force. evolutionary force.
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For a mutation to For a mutation to become significant, become significant, it must increase its it must increase its frequency, so that frequency, so that it becomes fixedit becomes fixed** in in the population. the population.
**frequency of allele = 1.0frequency of allele = 1.0