LinkedGenes Lecture12 me
GeneticLinkage
mendel'speas
menaelc rossbredsome28.000 gardenpeaplants
mendelfocusedon 7 discrete traits color shape podcolor podshape Howerc olorflower
position plantneight
DeviationfromMendelianprinciples
epigeneticmodifications couldresult in changes in thephenotype in a non mendelianmanner
liketurningoff expression ofoneallele Generegulationless
linkage ifsomegeneswerelinkedonthe same chromosome and coinherited not indassor
e
mostprominentexceptionto Mendel'sLawofindependent assortment
genesforhistraitswerefara partondiffchromosomes
If theywere onthesamechromosome and coinherited violatesexpectationof independentassortment
ThomasHuntM organ DrosophilaGenetics
Geneticlinkage demonstratedthatg enesarephysically locatedon chromosomes andthatthoselocatedclosetogethertendtobeinherited
together
hisstudent constructed ist geneticmap linkagemap
i tenameinheritedtogether
iii iii a
int int aini ainiiieiamian i in
in fruitflyDrosophila 2genes whiteeyes w andcrossveinless wingscarsarelinkedonthe x chromosome
thealleles at these 2 genestendto beinheritedtogether
deviationfrommendelianratios
FortheFamaleoffspring youwouldexpect iii
ratiosof wear wear wout ww
if recombination werefreelyhappeningbetweenthese
g enes
the lackof independent assortmentmeansthat
the genes
snowlinkage
thefactthattheparentalcombinations
weaveand w w nweremuchmorecommon
indicatesthatrecombinationwasunableto
breakthoseanesesapart
overd uringmeiosisbreaksuplinkage
crossing
genessothatthenrecombine
crossingoverbreaksuplinkageamong
over exchangeof geneticmaterialbetweenhomologousbutnonsisterchromatidsduringmeiosis
crossing
recombination exchangeofgeneticmaterialb etweendifferent chromosomes inevicarnotes leadingtotheproduction of offspringwithnew
combinationsofallelesthatd ifferf rom thoseroundineitherparent
linkageandrecombination
crossingovercanleadto recombinationbetweenthealleles ofthegenes
butdoesnotalways
crossingoverb etweengenes resultsin recombination betweenthe anglesof
genes
whencrossingoveroccurso utsidetheintervalbetweenthegenesthereis no
recombination betweenthealleles of thegenes
GeneticLinkage
mendel'speas
menaelc rossbredsome28.000 gardenpeaplants
mendelfocusedon 7 discrete traits color shape podcolor podshape Howerc olorflower
position plantneight
DeviationfromMendelianprinciples
epigeneticmodifications couldresult in changes in thephenotype in a non mendelianmanner
liketurningoff expression ofoneallele Generegulationless
linkage ifsomegeneswerelinkedonthe same chromosome and coinherited not indassor
e
mostprominentexceptionto Mendel'sLawofindependent assortment
genesforhistraitswerefara partondiffchromosomes
If theywere onthesamechromosome and coinherited violatesexpectationof independentassortment
ThomasHuntM organ DrosophilaGenetics
Geneticlinkage demonstratedthatg enesarephysically locatedon chromosomes andthatthoselocatedclosetogethertendtobeinherited
together
hisstudent constructed ist geneticmap linkagemap
i tenameinheritedtogether
iii iii a
int int aini ainiiieiamian i in
in fruitflyDrosophila 2genes whiteeyes w andcrossveinless wingscarsarelinkedonthe x chromosome
thealleles at these 2 genestendto beinheritedtogether
deviationfrommendelianratios
FortheFamaleoffspring youwouldexpect iii
ratiosof wear wear wout ww
if recombination werefreelyhappeningbetweenthese
g enes
the lackof independent assortmentmeansthat
the genes
snowlinkage
thefactthattheparentalcombinations
weaveand w w nweremuchmorecommon
indicatesthatrecombinationwasunableto
breakthoseanesesapart
overd uringmeiosisbreaksuplinkage
crossing
genessothatthenrecombine
crossingoverbreaksuplinkageamong
over exchangeof geneticmaterialbetweenhomologousbutnonsisterchromatidsduringmeiosis
crossing
recombination exchangeofgeneticmaterialb etweendifferent chromosomes inevicarnotes leadingtotheproduction of offspringwithnew
combinationsofallelesthatd ifferf rom thoseroundineitherparent
linkageandrecombination
crossingovercanleadto recombinationbetweenthealleles ofthegenes
butdoesnotalways
crossingoverb etweengenes resultsin recombination betweenthe anglesof
genes
whencrossingoveroccurso utsidetheintervalbetweenthegenesthereis no
recombination betweenthealleles of thegenes
