Oneofthestagesofcelldivision(mitosisandmeiosis)duringwhichthecentromeressplitandhalfofeachchromosomepairmovesfromtheequatortothepolesofthecell.Thisisfollowedbytelophase.
anaphase
Mitosis.Nucleus(orDNAinbacteria)duplicatesandthenthecontentsofcelldivide.Cellelongates,andreplicatedDNAandcontentsarepushedaparttooppositeends.Cellmembraneconstrictsorcellwallforms,resultingintwodaughtercellsidenticalto,butonlyhalfthesizeof,theoriginalparentcell.ThistypeofreproductionisfoundintheProtistaandbacteria.
binaryfission
Agroupofdisorderscausedbytheabnormalanduncontrolleddivisionofcellsbymitosis,resultingfromthelossofcontrolovertheirrateofgrowthandcelldivision,formingatumourwhichtheninvadesthesurroundingtissues.
cancer
Anysubstancethatwillcauseanormalcelltobecomeacancercell,e.g.formaldehyde,carbontetrachloride,radiation,smokefromcigarettes,etc.
carcinogen
Cellssurviving,growinganddividingandbeingpassedfromonegenerationtothenext.
cellcontinuity
Thesequenceofstepsperformedbyacellinordertoreplicateitself(replication),fromonedivisionbymitosistothenext.ThecycleconsistsofagrowthperiodduringwhichthecellincreasesinsizefollowedbythereplicationofitsDNAandthedivisionofthecell(celldivision).
cellcycle
Theprocessbywhichnewcellsaremadefromexistingcells.
celldivision
Foundinmanynon-dividingcells.Duringmitosisitdoublesandmovestooppositesidesofthecellwhereitformsthepolesofthespindlefibres.
centriole
Pairsofchromatids(chromosomesinadividingcell)areheldtogetherbythis.Usedtoattachchromatids/chromosomestospindleduringmetaphaseofcelldivisions.
centromere
Thedividingofthecytoplasmofthecellintotwoduringtelophaseofmitosis.
cleavage
Thecellsproducedasaresultofdividingbymitosis.
daughtercells
Everyorganismhasafixednumberofchromosomes.Iftheyoccurinpairs(homologouspairs)theorganismissaidtobe...,i.e.twosetsofchromosomes–onesetreceivedfromthefatherandonesetfromthemotheratfertilisation,e.g.human2n=46,mouse2n=40,fruitfly2n=8.ORitcanbedescribesasdoublethenumberofchromosomesfoundingametes.
diploid
Amethodofasexualreproductionwhereacellororganismdividesintotwoormoreparts,e.g.binary...
fission
Anycellwhichmustfusewithanothercellinordertoproduceanewindividual.Isahaploidreproductivecell,i.e.containshalftherequiredgeneticinformationfortheformationofanewindividualorhalfthesomaticnumberofchromosomes(inhumans=23),e.g.spermcell,egg.
gamete
Havingoneofeachofthepairsofchromosomescharacteristicforaspecies.
OR
Halfthesomaticnumberofchromosomes.
OR
Asinglesetofunpairedchromosomes.
haploid
Apreparatorystagebeforeorarestingstageaftermitosisormeiosis.Itisfollowedbyprophase.
interphase
Acelldivisionofgameteorsporeproducingcells.Cantakeplaceindiploidcellsonly.Producesfourcellsthatmayallbedifferentgenetically.Daughtercellshavehalfthenumberofchromosomesastheparentcell.Ithelpstomaintainthechromosomenumberoftheparentbyproducinghaploidgametesinsexualreproduction.Italsointroducesvariationsintoaspeciesbymixingthegeneticmaterialthatpassesontothenextgeneration.
meiosis
Stageduringmitosisandmeiosisduringwhichthechromosomes(=onepairofchromatids)becomeattachedtothespindlefibresbytheircentromeresandbecomealignedinanequatorialplaneperpendiculartothespindleaxis.Thisisfollowedbyanaphase.
metaphase
Usualmethodofcelldivisionbycellsnotinvolvedintheformationofgametes(somaticcells).Ittakesplaceinhaploidanddiploidcells.Itproducestwodaughtercellswhicharegeneticallyidenticalandhavethesamenumberofchromosomesastheparentcell.Thedaughtercellsaresmallerinsizethantheparentcell. Itisamethodofreproductioninunicellularorganismsbutismainlyforgrowthandrepairinmulticellularorganisms.
mitosis
Havingmorethantwoofeachgene,ormorethantwosetsofchromosomes,e.g.3n(triploid),4n(tetraploid).
polyploid
Rapidgrowthbyactivecelldivision.
proliferation
Thefirststageofcelldivision(mitosisandmeiosis).Chromatinthreadsshortenandthickentobecomevisibleaschromosomes.Theseduplicatetoformchromatids(heldtogetheratcentromere).Nuclearmembranedisappearsandspindlefibresform.Thisisfollowedbymetaphase.
prophase
Duringmetaphaseofmitosisandmeiosis,itisthethreadlikestructureformedfrompoletopoleinthecellforchromosomestobecomeattachedto.
spindle(fibres)
Thefinalstageofmitosisandmeiosiswhenthenewnucleiareformedandthecytoplasmofthecelldivides,bytheformationofacleavagefurrowinanimalcellsandtheformationofacellplateinplantcells.Thisisfollowedbyinterphase.
telophase
Swellingduetoabnormalgrowthofcells.
tumour