Mitotic Cell division

Mitosis

1. Mitotic Cell Division
Mr.BinuBabu
MBA, M.Sc. (N)
Asst. Professor
Mrs. JincyEalias
M.Sc. (N)
Asst. Professor

2. Mostcellsofthehumanbodyundergocell
division,theprocessbywhichcells
reproducethemselves.
•Thetwotypesofcelldivision—
–Somaticcelldivision(mitoticdivisionor
mitosis)
–Reproductivecelldivision(meioticdivisionor
meiosis)

3. Somatic cell division
•Acellundergoesanucleardivisioncalled
mitosis
•Acytoplasmicdivisioncalledcytokinesis
•Thistwoprocessproducetwogenetically
identicalcells,eachwiththesamenumberand
kindofchromosomesastheoriginalcell.
•Somaticcelldivisionreplacesdeadorinjured
cellsandaddsnewonesduringtissuegrowth.

4. Reproductive cell division
•Itisthemechanismthatproducesgametes,
thecellsneededtoformthenextgeneration
ofsexuallyreproducingorganisms.
•Thisprocessconsistsofaspecialtwostep
divisioncalledmeiosisinwhichthe
numberofchromosomesinthenucleusis
reducedbyhalf.

5. •Thecellcycleistheseriesofchangesacell
goesthroughfromthetimeitisformeduntil
itreproduces.
•Thetwomajorperiodsofthecellcycle:
–Interphase:-inwhichthecellgrowsandcarries
onitsusualactivities
–Celldivisionorthemitoticphase:-duringwhich
itdividesintotwocells

7. Interphase
•DuringinterphasethecellreplicatesitsDNA,italso
producesadditionalorganellesandcytosoliccomponentsin
anticipationofcelldivision.
•Interphaseisastateofhighmetabolicactivitybutcelldoes
notgrow.
•Interphaseconsistsofthreephases
–G1:-itistheintervalbetweenthemitoticphaseandtheS
phase
–Sorsynthesis:-DNAreplicationoccurs
–G2istheintervalbetweentheSphaseandthemitotic
phase
G
0:-CellsthatremaininG1foraverylongtime,perhaps
destinednevertodivideagain.

9. •G1Phase:-Itistheintervalbetweenthe
mitoticphaseandtheSphase.
•Thecellismetabolicallyactive;itreplicates
mostofitsorganellesandcytosolic
componentsbutnotitsDNA.Replicationof
centrosomesalsobeginsintheG1phase.

10. •TheSphase,theintervalbetweenG1and
G2,lastsabout8hours.DuringtheSphase,
DNAreplicationoccurs.
•AsaresultofDNAreplication,thetwo
identicalcellsformedduringcelldivision
laterinthecellcyclewillhavethesame
geneticmaterial.

11. •TheG2phaseistheintervalbetweentheS
phaseandthemitoticphase.Itlasts4to6
hours.
•DuringG2,cellgrowthcontinues,enzymes
andotherproteinsaresynthesizedin
preparationforcelldivision,andreplication
ofcentrosomesiscompleted.

12. NUCLEARDIVISION:MITOSIS
•Mitosis,asnotedearlier,isthedistributionof
twosetsofchromosomesintotwoseparate
nuclei.
•Theprocessresultsintheexactpartitioningof
geneticinformation.
•Theprocessisdividedintofourstages:
–Prophase
–Metaphase
–Anaphase
–Telophase

13. Prophase
•During early prophase, the chromatin fibers
condense and shorten into chromosomes.
•The condensation process may prevent
entangling of the long DNA strands as they
move during mitosis.

15. Metaphase
•Duringthisphase,themicrotubulesofthe
mitoticspindlealignthecentromeresofthe
chromatidpairsattheexactcenterofthe
mitoticspindle.
•Thismidpointregioniscalledthemetaphase
plate.

17. Anaphase
•Duringthisphase,thecentromeressplit,
separatingthetwomembersofeach
chromatidpair,whichmovetoward
oppositepolesofthecell.
•Onceseparated,thechromatidsaretermed
chromosomes.
•Asthechromosomesarepulledbythe
microtubulesofthemitoticspindleduring
anaphase,theyappearV-shaped.

19. Telophase
•Thefinalstageofmitosis,telophase,begins
afterchromosomalmovementstops.
•Theidenticalsetsofchromosomes,nowat
oppositepolesofthecell,uncoilandrevert
tothethreadlikechromatinform.
•Anuclearenvelopeformsaroundeach
chromatinmass,nucleolireappearinthe
identicalnuclei,andthemitoticspindle
breaksup.

22. CYTOPLASMIC DIVISION: CYTOKINESIS
•Divisionofacell’scytoplasmandorganelles
intotwoidenticalcellsiscalledcytokinesis.
•Thisprocessusuallybeginsinlateanaphase
withtheformationofacleavagefurrow,a
slightindentationoftheplasmamembrane,
andiscompletedaftertelophase.