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Name_______________________________________________________________Period______Date____________ KaryotypeAnalysis Background: Akaryotypeisapictureinwhichthechromosomesofacellhavebeenstainedsothatthebandingpatternofthe chromosomesappears.Cellsinmetaphasearestained,andthenphotographedthroughthemicroscopeandthe photographisenlarged.Thechromosomesarecutfromthephotographandarrangedinpairsaccordingtosizeand centromereposition.Karyotypeshavebecomeofincreasingimportancetogeneticcounselorsasdisordersanddiseases havebeentracedtospecificvisibleabnormalitiesofthechromosomes. Purpose: Researchershavebeenstudyingapopulationofrareinsects,Insectushighschoolus,foundonlyontheInderkumHigh Schoolcampus.Theresearchershaveobservedvariousformsoftheinsectsandhaveconcludedthatmayoftheseforms aretheresultofgeneticdisorders. Oneresearcherfoundasampleofsixpartiallydigestedindividualsinthestomachofaseagull(thatwasfounddead). Becausetheseinsectswerepartiallydigested,theappearanceoftheindividualscouldnotbedetermined,although mostofthebodiesremained.Undigestedcellsamplesofeachindividualweretakentodeterminethekaryotypes. Youwillpreparethekaryotypesoftheinsectsandanalyzethemforchromosomalabnormalities.Furthermore,youwill identifythedisordersbasedonyouranalysisandtrytofigureouthowakaryotypeanalysiscanbeusedtoexplainthe presenceofageneticdisorder. Procedures 1. Studythekaryotypesandphenotypes(physicalcharacteristics)ofanormalmaleandfemaleinsect. Note:thenormalmaleandfemaleinsect’sthirdpairofchromosomesaresexchromosomes.Thesechromosomes aresimilartothatofhumans;themalehasonesmallandlargesexchromosome(XY)andthefemalehastwolarge sexchromosomes(XX)(Figure1). 2. Studytheobservedgeneticdisordersthattheinsectshave: a. Sizereductiondisorderappearswhenthereisamonosomy ofthesexchromosomepair.Asinglelargechromosome producesasmallfemaleinsect.Asinglesmallchromosome producesasmallmaleinsect(Figure2). b. Clear-wingdisorderappearstoresultfromtrisomyofthe chromosomesofthesecondpair.Theextrachromosomeof thesecondpairproducessterileinsectsthatlackcoloringin theirwings.Sincesterilityalwaysresults,theclear-wing disorderisnotpassedontoprogeny(Figure3). c. Duplicationdisorderappearswhenaportionofa chromosomeinthefirstpairhasbeenduplicated.This disorderresultsintwoheads,abandingpatternonthe wings,andadditionalbodysegments(Figure4). d. Unsegmenteddisorderappearswhenasmallsegmentof thesexchromosomeisdeleted.Theresultsarealossof bodysegmentationandreductionofbodysize.(Figure5) 3. Obtaincopiesofthemetaphasechromosomesofsixinsects. 4. Cutoutthechromosomesforinsect1fromthephotocopyand placethemalongthelineforinsect1inDataandObservations. 5. Arrangesimilarchromosomestogetherasshowninthenormal karyotypesinFigure1. 6. Matchupsimilarchromosomesbycomparingchromosomesize, lengthofthearmsofeachchromosome,centromereposition andbandingpatterns. 7. Besuretolineupchromosomesthatresemblethefirstpairof thenormalkaryotypeabovenumber1,thosethatresemblethe secondpairabovenumber2andthosethatresemblethethird pair(sexchromosomes)abovenumber3. 8. Oncethechromosomesarepositioned,pastetheircentromeres tothestraightline.Thisrepresentsthekaryotypeforoneinsect. 9. Repeattheabovestepsforeachoftheremaininginsects. 10. Compareyourkaryotypeswiththekaryotypesofthenormal insectsandwiththedescriptionsofthegeneticdisorders. 11. CompletetheAnalysisQuestions. DataandObservations: Insect1 _________________________________________ 1 2 3 Insect3 _________________________________________ 1 2 3 Insect5 _________________________________________ 1 2 3 Insect2 _________________________________________ 1 Insect4 _________________________________________ 1 Insect6 _________________________________________ 1 2 2 2 3 3 3 AnalysisQuestions: 1. Identifythesex,geneticdisorderandchromosomeerrorforeachoftheinsects. Sex GeneticDisorder ChromosomalError Insect1 Insect2 Insect3 Insect4 Insect5 Insect6 2. Whichtypeofchromosomeabnormalitywasthemostdifficulttodetectthroughthekaryotype?Theeasiest? 3. Howcanaduplicationofthefirstchromosomepairproduceadoubleheadandatthesametimeaffectthewing pigmentationandbodysegments? 4. Whatkindofinformationwouldberequiredifakaryotypeanalysiswereusedtodetectthegeneticdisorderofa realorganism? 5. Howcankaryotypeanalysisbeusedtoexplainthepresenceofageneticdisorder?
