Download ChromoSock Mitosis Instructor Protocol

ChromoSockMitosis
InstructorProtocol
Overview
Inthisactivity,studentswilluseChromoSockstomodelthebehaviorofchromosomesduringmitosis.
Studentswillsimulatethemovementofchromosomesduringcelldivision.Usingaphysicalmanipulative
likeChromosocksprovidesvisualcluesofstudentconceptsthatcanbeusedtoaddresscommon
chromosomemisconceptions
LearningObjectives:
Definehaploidanddiploid
Identifychromosomenumberatseveralpointsduringmitosis
Identifymitosisasthedivisionthatproducesidentical‘daughtercells’
Modelmitosis
Correctlylabelcentromere,chromosome(bothreplicatedandnon-replicated)andchromatidsinadiagram
Materials
2BagsofChromosocksforeachpairofstudents.Eachbagcontains:
1whiteChromoSockwithanorangestripelabeled“F”
1whiteChromoSockwithanorangestripelabeled“f”
1beigeChromoSockwithagreenstripelabeled“B”
1beigeChromoSockwithagreenstripelabeled“b”
1greyChromoSockwithablackstripelabeled“N”
1greyChromoSockwithablackstripelabeled“n”
Rubberbands
ChromoSockWorksheet
Timeframe
Thisactivityisdesignedtobecompletedinasingleclassperiod.
© 2016 HudsonAlpha Institute for Biotechnology
IntroducingMitosis
1.DistributeabagcontainingonesetofChromoSockstoeachpair(group)ofstudents.
RemindstudentsthatDNAisfoundinthenucleusofeachcell.Somatic(allbodycells,except
reproductivecells)cellsundergomitosis.
2.DirectstudentstoremovetheChromoSocksandarrangeinpairs.Chromosomes,likesocks,occurin
pairs.Thesepairsarecalledhomologs.Studentswilldrawthecellandlabelthechromosomeploidyand
number.Studentsaretousean“I”shapetorepresentasinglechromosome;laterintheactivityan“)(”
shapewillbeusedtorepresentareplicatedchromosome.
Remindstudentsthateachindividualhasonecompletesetofchromosomes,halfofwhichcamefrom
motherandtheotherhalffromfather.Pointoutthatalthoughthesocksmayappearslightlydifferent,
onecaneasilydeterminewhichtwoshouldbepaired.Askstudentsiftheycanidentifywhichofeachpair
ofchromosomescamefromthefatherandwhichcamefromthemother.Answer:No.
Askstudentshowmanytotalchromosomesarepresent?Answer:6(six).
Askhowmanypairsofchromosomesarepresent.Answer:3(three).Thesecellsarediploidandthe
diploidchromosomenumberis6forthishypotheticalorganism.
Usingthechartoforganismsbelow,exploreconceptsofdiploidandhaploidchromosomenumberwith
students.
Chromosomenumberacrossvariousorganisms
Organism
CommonName
DiploidChromosome#
Giraffacamelopardalis Giraffe
62
Pantheraleo
Lion
38
Zeamays
Maize/Corn
20
Ananascomosus
Pineapple
50
Lumbricusterrestris
Earthworm
36
3.TheChromosockswillnowbeusedtomodelthephasesofmitosis.
Askstudentswhatmustoccurbeforeacellcanenteranytypeofcelldivision.Answer:DNAmustbe
copiedorreplicatedsothateachcellreceivesacopyofthemasterinstructions.
© 2016 HudsonAlpha Institute for Biotechnology
4.DistributeabagcontainingasecondsetofChromoSockstoeachpair(group)ofstudents.Thebag
containsthematerialsneededtoreplicatetheChromosocks.
5.Discussreplicatedchromosomes.Studentswillchooseareplicatedchromosomeintheirsketchand
labelthefollowing:centromere,chromosomeandchromatid.
Introducethevocabularyterms“replicatedchromosome”and“sisterchromatid”.Pointoutthat
althoughthereplicatedchromosomecontainstwosisterchromatids,itstillbehavesasasingle
chromosomeduringmostofmitosis.
6.Directstudentstomatchthematerialsfromthesecondsetwiththesockchromosomepairsontheir
deskfromthefirstbag.Attachpairsofsockswithrubberbandssimulatingtheconnectionbetweensister
chromatidsatthecentromere.StudentswillsketchthecellfollowingDNAreplication.Studentswilllabel
thechromosomeploidyandnumber.Theywillusean“)(“shapetoindicateeachreplicatedchromosome
inthesketches.Studentswillchooseareplicatedchromosomeintheirsketchandlabelthefollowing:
centromere,chromosomeandchromatid.
Askstudentshowmanychromosomesarepresent.Answer:Six,eachofthereplicatedchromosomesis
stillcountedasasinglechromosome.Encouragestudentstocountthenumberofcentromeresrather
thanthenumberofsisterchromatidstogetanaccuratechromosomecount.
Mitosis
7.ThefollowingstepsillustratehowtousetheChromoSockstomodelmitosis.
8.Atthebeginningofmitosis,thereisonepileofChromoSocksrepresentingthechromosomesinthe
nucleusofasinglecell.Directstudentstolineupthepairsalongthemiddleofthedeskortableto
representhowchromosomeslineupalongtheequatorofthecell(Metaphase).Studentswillsketchthe
chromosomesinthecell.
ExplainthatduringMetaphasethespindlefibersareattachedtothecentromereofeachchromosome.
Thecentromeresofthesisterchromatidsbehaveindependentlyatthisstep,withaspindlefiberfrom
onepoleattachingtothecentromereofonesisterchromatidandthecentromereoftheothersister
chromatidattachingtoaspindlefiberfromtheoppositepole.
© 2016 HudsonAlpha Institute for Biotechnology
9.Directstudentstoremovetherubberbands,simulatingthephysicalchangeinthecentromerethat
allowschromatidstoseparate.Atthispoint,thereplicatedchromosomenolongerbehavesasasingle
unit.SeparatethesisterchromatidsbymovingoneofeachoftheChromoSockstotheoppositesideof
each‘cell’(Anaphase).Studentswillsketchthechromosomesattheendoftheprocess.
Remindstudentsthatoncesisterchromatidsseparate,thechromosomesshouldbesketchedas“I”
shapesratherthan“)(”shapes.
10.HavestudentscollecttheChromoSocksintoatightbundlesimulatingthereformingofthenuclear
membrane(Telophase).
Explainthatcytokinesisoccurs,dividingeachcellintotwonewcells.Askstudentshowmanycellsare
formedbythecompletedprocess?Answer:two.
11.Havestudentscarefullycountthenumberofchromosomesineachnewcell.Theywillthensketchthe
chromosomesineachcellandlabelthechromosomeploidyandnumberbesideeachsketch.
Theyshouldthenanswerthefollowing:Howdoesthechromosomenumbercomparetotheoriginalcell?
Howdothetypesofchromosomespresentcomparetotheoriginalcall?
Askstudentshowmanychromosomesarefoundineachnewcell?Answer:SixAskhowthesecells
comparetotheoriginalcell?Answer:exactlythesameinchromosomenumberandtype.
12.StudentsshouldreplacetheChromoSocksinthebags.Eachbagshouldcontain2long,2mediumand2
shortChromoSocks.
CarefullymonitorstudentsastheyreplaceChromoSocksinthebags.
© 2016 HudsonAlpha Institute for Biotechnology