Duplications can affectphenotype(a)Duplicationheterozygositycancausevisiblephenotypes.Novel phenotypesAberrantwingveinsMore gene copies.Wild-type wing:ThreecopiesofNotch+geneGenes next totwocopiesofNotchtgeneduplicationdisplacedto(b)Forraregenes,survival requiresexactlytwocopies.new environmentTol++Living flyaltering expression(twocopiesTp/+)+TOeDelLethal(onecopyTp/+)+DpDLethalDrosophila(threecopies Tp/+)+Triplolethal (Tpl+)locusDpLiving fly(two copies Tpl+)Del
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 14-16 Duplications can affect phenotype Duplications can affect phenotype Novel phenotypes Novel phenotypes More gene copies. More gene copies. Genes next to Genes next to duplication displaced to duplication displaced to new environment new environment altering expression. altering expression. Drosophila Triplolethal (Tpl+) locus
PhenotypeGenotypeofXchromosomesWild-typeeye16AWildtypeUnequal16A116ABarcrossing overBareyebetween16AT16AT16ADouble-BarduplicationsOut-of-register pairingincreases orduringmeiosis in a Bar-eyedfemaleDouble-Bareye16AL16Adecreases genecopy number16AL16ANumberof16Aregions increased;Numberof16Amoreborderregionsregionsdecreased;no borderregion16A116AT16A16ADpbreakpointcausesBar-eyedphenotypeA6Bar gene codingEnhancerregion14-17Fig.12.10
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 14-17 Unequal Unequal crossing over crossing over between between duplications duplications increases or increases or decreases gene decreases gene copy number copy number Fig. 12.10
3. Inversions reorganize the DNA seguence of a chromosome(a)Chromosomebreakagecanproduceinversions.Produced by halfPericentricinversionParacentricinversionrotation ofPointsofbreakagePoints of breakagechromosomalregionsABCDEBCDEafter double-stranded180°rotation180°rotationbreak.DCBEDCBEAlso byrarecrossoverbetween related genes(b)Intrachromosomalrecombinationcanalsocauseinversions.in oppositeFDWild-typeorientation orchromosometransposition.EBCDAB4KDCBAInversionFig. 12.1114-18
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 14-18 3. Inversions reorganize the DNA sequence of a chromosome 3. Inversions reorganize the DNA sequence of a chromosome Produced by half Produced by half rotation of rotation of chromosomal regions chromosomal regions after double after double-stranded stranded break. Also by rare crossover Also by rare crossover between related genes between related genes in opposite in opposite orientation or orientation or transposition. transposition. Fig. 12.11
An inversion can affect phenotype if it disrupts a gene(c) Inversions can disruptgenefunction.BreakpointBreakpointygeneWildtype180°rotationInversionIn(1)v4Drosophilayellow(y)gene14-19Fig.12.12
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 14-19 An inversion can affect phenotype if it disrupts a gene An inversion can affect phenotype if it disrupts a gene Fig. 12.12 Drosophila yellow (y+) gene
Inversion heterozygotes produce few, if anyrecombinantprogenyBcDAECOBDEAPericentricNormalchromosomeinversion-aDaGdCbaNormalgameteheterozygoteInvertedchromosome8APairingduringRecombinantmeiosis1gameteswithduplicationand deletionCrossoverDininversion-CloopC.Inversiongamete二ECompletionofbothmeioticdivisionsFig.12.1414-20
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 14-20 Inversion Inversion heterozygotes heterozygotes produce few, if any, produce few, if any, recombinant progeny recombinant progeny Fig. 12.14 Pericentric inversion heterozygote