Cellular Reproduction
AND WHATITACCOMPLISHES
reproductionoccursatthecellularlevel
reproduction EXAMPLE liketheskinonyourarm skincellsareconstantlyreproducing
themselvesandmovingtowardtheoutersurfacereplacingdeadcellsthathaverubbed
offthisremovaloftheskingoesonthroughoutlifeandwhentheskingetsinjured
thereproductionofcellsiswhathelpstohealthewound
MM I3whenacellundergoesreproductiontheprocess is called
celldivisionThe 2daughtercellsthatresultfromcelldivisionaregenetically
identicaltoeachotherandtotheoriginal parent cellBeforetheparentcell
splitsin 2 itduplicateschromosomesandthenduringcelldivisioneach
daughtercellreceivesoneidenticalsetofchromosomesfromtheoriginal
parentcell
celldivisionplaysseveralImportantrolesinthelivesof organisms
thefunctionsof EXAMPLE withinthebodymillionsofcellsmustdivide
celldivision everysecondtoreplacedamaged orlostcells
anotherfunctionofcelldivisionISgrowth
all ofthemanycellsinyourbodyaretheresultof
repeatedcelldivisionsthatbeganinthemother'sbody
w asinglefertalizedegg
reproductionisanothervitalfunctionofcelldivision Manysingle
celledorganisms likeamoebasreproducebydividinginhalfandthe
offspringaregeneticreplicasoftheparent
Gthisis asexualreproduction
asexualreproduction thecreationofgeneticallyidenticaloff
byasingleparentwithouttheparticipationofspermandegg
offspringproduced
by asexualreproduction
asexualreproduction inheritalltheirchromosomesfromasingle
parentandthereforetherearegeneticduplicates
Anindividualthatreproducesasexuallygivesrise
toaclone agroupofgeneticallyidenticalindividuals
manymulticellularorganismscanreproduceasexuallyaswell
EXAMPLE Someseastarspeciescangrownewindividuals
fromfragmentedpieces or ingrowinghouseplantsfrom
clippings asexualreproductioninplants
in asexualreproductionthereisonesimpleprincipleofinheritance
Theloneparentandeachofitsoffspringhaveidentical
genesThetypeofcelldivisionresponsibleforasexualre
productionandforthegrowth4maintenance ofmulticellular
organismsiscalledmitosis
sexualreproductionrequiresthefertilizationofaneggby asperm
theproductionofgametes sperm egg meiosis
sexualreproduction 6meiosis
a aspecialkindofcelldivisionthatonly
occursinreproductiveorgans
thelifecycleofamulticellularorganismisthesequenceofgeneration
meiosis togenerationstagesfromfertilizationtotheproductionofitsownoffspring
GAMETES THELIFE thekeyfactortothelifecycleishaving2setsofchromosomesone
CYCLEOFASEXUALORGANISM Inheritedfromeachparent
humansarediploidorganismsbc
alltypicalbodycellssomaticcells
containpairsofhomologous
chromosomesmatchingsets
thegameteseggandspermcells
aren'tdiploid
I madebymeiosisin
anovaryortestis
a eachgametehasasingle
setofchromosomes 22
autosomes t lsexchrom
CRIMIFEE Someeitherxory
www asinglecell
chromosomesetisahaploidcell Itonly
hasonepairofhomologous
chromosomesfertilizationcycleahaploidspermfusesw ahaploidegg
theresultingfertilizedeggzygote diploidegg
Ithas2Setsofchromosomesonesetfromeachparent
Thelifecycleiscompletedasasexuallymatureadult
developsfromthezygote
mioticcelldivisionensuresthatallsomaticcellsofthehumanbody
receiveacopyofallofthezygote's46chromosomes everyoneof
thetrillionsofcellsinthebodycantraceitsancestrybackthrough
mioticdivisionstothesinglezygoteproduced
producinghaploidgametesbymeiosiskeepsthechromosome from
doublingineverygeneration
EXAMPLE
HOWMEIsosisHALVES
CHROMOSOMENUMBER
meiosisproduceshaploidgametesindiploidorganisms
theprocessof duringmeiosisthenumberofchromosomesiscutinhalf
meiosis inmeiosis acellthathasduplicateditschromosomesundergoes 2
consecutivedivisions meiosis1andmeiosis11
eachofthe4daughtercellsresultingfrommeiosishasahaploidsetof
chromosomes 42asmanychromosomes asthestartingcell
GBthisisb coneduplicationofthe
chromosomesISfollowed
by2divisions
meiosisalsoinvolvesanexchangeofgeneticmaterial piecesof
chromosomesbetweenhomologouschromosomes
thisexchangeiscalledcrossingoverwhichisthefirstpro
phaseofmeiosis
STAGESOFMEIOSIS
benigntumoralumpofabnormalcellsthatremainsattheoriginal
cancer siteeventhoughitgrowsoutofcontrol
malignanttumor anabnormallygrowingmassofcellsactivelyspreading
throughthebody
metastasisthespreadofcancercellsfromtheiroriginsitetoothersites
anindividualw amalignanttumorissaidtohavecancer