Chapter 3: Transmission genetics: The principle of segregation Overview Mendel’s laws Segregation of a single gene Segregation of a single gene Segregation of two or multiple genes H di l i Human pedigree analysis Probability in genetic analysis Monogenic and oligogenic inheritance Overview Mendel’s laws Segregation of a single gene Segregation of a single gene Segregation of two or multiple genes H di l i Human pedigree analysis Probability in genetic analysis Monogenic and oligogenic inheritance Mendel’s laws Segregation of a single gene Experimental design Observation: phenotypic ratios in F2’s Observation: phenotypic ratios in F2 s Mendel’s “gene” model Testing the model: F3 & testcross Equivalence of reciprocal crosses Equivalence of reciprocal crosses Morphological versus molecular h t phenotypes
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Chapter 3:
Transmission genetics:The principle of segregation
Overview
Mendel’s lawsSegregation of a single geneSegregation of a single geneSegregation of two or multiple genes
H di l iHuman pedigree analysisProbability in genetic analysisy g yMonogenic and oligogenic inheritance
Overview
Mendel’s lawsSegregation of a single geneSegregation of a single geneSegregation of two or multiple genes
H di l iHuman pedigree analysisProbability in genetic analysisy g yMonogenic and oligogenic inheritance
Mendel’s lawsSegregation of a single gene
Experimental designObservation: phenotypic ratios in F2’sObservation: phenotypic ratios in F2 sMendel’s “gene” modelTesting the model: F3 & testcrossEquivalence of reciprocal crossesEquivalence of reciprocal crossesMorphological versus molecular h tphenotypes
Experimental designp gPea cultivation
Experimental designp gPure lines
Experimental designp gSelfing vs outcrossing
Mendel’s lawsSegregation of a single gene
Experimental designObservation: phenotypic ratios in F2’sObservation: phenotypic ratios in F2 sMendel’s “gene” modelTesting the model: F3 & testcrossEquivalence of reciprocal crossesEquivalence of reciprocal crossesMorphological versus molecular h tphenotypes
ObservationsPhenotypic ratio in F2’s
Mendel’s lawsSegregation of a single gene
Experimental designObservation: phenotypic ratios in F2’sObservation: phenotypic ratios in F2 sMendel’s “gene” modelTesting the model: F3 & testcrossEquivalence of reciprocal crossesEquivalence of reciprocal crossesMorphological versus molecular h tphenotypes
Mendel’s modelSegregation of gene particules
Mendel’s lawsSegregation of a single gene
Experimental designObservation: phenotypic ratios in F2’sObservation: phenotypic ratios in F2 sMendel’s “gene” modelTesting the model: F3 & testcrossEquivalence of reciprocal crossesEquivalence of reciprocal crossesMorphological versus molecular h tphenotypes
Testing the modelgF3
Testing the modelgTestcross
Testing the modelgTestcross
Mendel’s lawsSegregation of a single gene
Experimental designObservation: phenotypic ratios in F2’sObservation: phenotypic ratios in F2 sMendel’s “gene” modelTesting the model: F3 & testcrossEquivalence of reciprocal crossesEquivalence of reciprocal crossesMorphological versus molecular h tphenotypes
Equivalence of reciprocal q pcrosses
Mendel’s lawsSegregation of a single gene
Experimental designObservation: phenotypic ratios in F2’sObservation: phenotypic ratios in F2 sMendel’s “gene” modelTesting the model: F3 & testcrossEquivalence of reciprocal crossesEquivalence of reciprocal crossesMorphological versus molecular h tphenotypes
Molecular versus morphological p ggenotypes
Molecular versus morphological p ggenotypes
Overview
Mendel’s lawsSegregation of a single geneSegregation of a single geneSegregation of two or multiple genes
H di l iHuman pedigree analysisProbability in genetic analysisy g yMonogenic and oligogenic inheritance
Mendel’s lawsSegregation of 2 or more genes
Observation: independent phenotypic assortmentassortmentMendel’s model: independent seg egationsegregationTesting the modelThree or more genes
Observation: independent pphenotypic assortment
Mendel’s modelindependent segregation
Mendel’s modelindependent segregation
Testing the modelgtestcross
Three or more genes Overview
Mendel’s lawsSegregation of a single geneSegregation of a single geneSegregation of two or multiple genes
H di l iHuman pedigree analysisProbability in genetic analysisy g yMonogenic and oligogenic inheritance
Human & animal pedigree analysis
Drawing pedigreesCharacteristics of dominant and Characteristics of dominant and recessive inheritanceMost human genetic variation is not “bad”
Drawing pedigrees
Dominant in heritance Dominant inheritance
Males and females are equally affectedaffectedAffected have one affected parent, eq all likel to be fathe o mothe equally likely to be father or mother (! neomutations) On average, half the offspring of an affected parent are affectedp
Recessive inheritance Recessive inheritanceMales and females are equally likely to be affectedAffected individuals, if fertile, usually have no affected offspringMost affected individuals have unaffected parentsh f ff d d d l fThe parents of affected individuals are often
related (consanguinous matings or inbreeding)A t ibli f ff t d i di id l th Amongst siblings of affected individuals, the proportion of affected is ∼ ¼.
Most human genetic variation is gnot “bad”
DNA sequence polymorphisms segregate according to Mendel’s lawsMost polymorphisms are “neutral” …… but, phenotypes that segregate according to Mendel’s laws are primarily:
Humans: inherited defectsD ti i lDomestic animals:
Inherited defectsSelected “attributes”: e.g. coat color, horns …g ,
Mendelian segregation of a g gVNTR
Most human genetic variation is gnot “bad”
DNA sequence polymorphisms segregate according to Mendel’s lawsMost polymorphisms are “neutral” …… but, phenotypes that segregate according to Mendel’s laws are primarily:
Humans: inherited defectsD ti i lDomestic animals:
Inherited defectsSelected “attributes”: e.g. coat color, horns …g ,
Overview
Mendel’s lawsSegregation of a single geneSegregation of a single geneSegregation of two or multiple genes
H di l iHuman pedigree analysisProbability in genetic analysisy g yMonogenic and oligogenic inheritance
Probability in genetic analysis
DefinitionsProbability of the union of eventsProbability of the union of eventsProbability of the intersection of eventsConditional probability and Bayes p y ytheorem
Probability in genetic analysisy g yDefinitions
Elementary outcomeProbability of elementary outcomesProbability of elementary outcomesSample space
E tEventProbability of an event
Elementary outcomes and ysample space Event
EventProbability in genetic analysisy g yUnion of events
Probability in genetic analysisy g yUnion of events
Probability in genetic analysisy g yIntersection of events
Probability in genetic analysisy g yIntersection of events
{ } { } { }BPAPABP ={ } { } { }BPAPABP =
Conditional probability and p yBayes theorem
{ } { }{ }ABPBAP =|{ } { }BP
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{ } { }{ } { }'|
AAABPBAP ={ } { } { }'|
BAPBAP +
{ } { } { }{ } { } { } { }
|| ABPAPBAP ={ } { } { } { } { }'|'||
ABPAPABPAP +
Overview
Mendel’s lawsSegregation of a single geneSegregation of a single geneSegregation of two or multiple genes
H di l iHuman pedigree analysisProbability in genetic analysisy g yMonogenic and oligogenic inheritance: complications to Mendel’s inheritance: complications to Mendel s rules