cell cycle & division

8/7/2019 CELL CYCLE & DIVISION

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Elwathiq Khalid Ibrahim

University of Kassala

Department of AnatomyDecember 2010

CELL CYCLE & CELL DIVISION


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Cell Cycle

Stages in growth &

division

G1 Phase

S Phase

G2 Phase

M PhaseCytokinesis


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LE 12-5

G1

G2

S

(DNA synthesis)

INTERPHASE


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G1 Phase

First growth stage

Cell increasesin sizeCell preparestocopyits DNA


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Synthesis Phase

Copyingofall ofDNAs

instructionsChromosomes duplicated


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G2 Phase

Time between DNA synthesis

& mitosisCell continuesgrowing

Needed proteins produced


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M Phase

Cell growth & proteinproduction stop

Cells energyusedtomake 2daughtercells

Calledmitosisor

karyokinesis (nucleardivision)


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Life Cycle of a Cell

Mitosisisacyclewithno beginningor end.


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Interphase Resting Stage

Cellscarryingonnormal

activities

Chromosomesarentvisible

Cell metabolismisoccurring

Occurs beforemitosis


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MITOSIS


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Mitosis

The process of cell division which results in the

production of two daughter cells from a single

parent cell.

The daughter cells are identicalto oneanother and to the original parent cell.


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copyright cmassengale13

Parent CellParent Cell

TwoTwo

identicalidentical

daughterdaughtercellscells

Identical Daughter CellsIdentical Daughter Cells


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Mitosis can be divided into stages

Interphase

Prophase

Metaphase

Anaphase

Telophase & Cytokinesis


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Interphase

The cell prepares for division

y Animal Cell

y DNA replicated

y Organelles replicated

y Cell increases in size


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Interphase

Animal Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm


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Prophase

The cell prepares for nuclear division

y Animal Cell

y P

ackages DNA intochromosomes


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ProphaseAnimal Cell Plant Cell



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Metaphase

The cell prepares chromosomes for

divisiony Animal Cell

y Chromosomes line up at the

center of the celly Spindle fibers attach from

daughter cells to

chromosomes at the

centromere


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Sketch The SpindleSketch The Spindle



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Metaphase

Animal Cell



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Anaphase

The chromosomes divide

y Animal Cell

y Spindle fibers pull

chromosomes apart

y of each chromosome(called chromotid) moves to

each daughter cell


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Anaphase

Animal Cell Plant Cell



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Telophase

The cytoplasm divides

y Animal Cell

y DNA spreads out

y 2 nuclei form

y Cell wall pinches in to formthe 2 new daughter cells


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Telophase

Animal Cell Plant Cell



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Cytokinesis

Occursafterchromosomes

separateFormstwo,identical

daughtercells


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Cytokinesis

Cell PlateFormingin PlantCells


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Animal Mitosis -- Review

Interphase Prophase

Metaphase Anaphase

Telophase Interphase


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LE 12-4

Chromosome

duplication

(including DNA

synthesis)

0.5 m

Centromere

Sister

chromatids

Separation

of sisterchromatids

Centromeres Sister chromatids


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Male Karyotype


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Human female karyotype


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MEIOSIS


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Meiosis

Meiosis is the type of cell division by which germ cells

(eggs and sperm) are produced.

One parent cell producesfourdaughter cells.

Daughter cells have half the number ofchromosomes found in the original parent cell


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Meiosis

but,onceDuring meiosis, DNA replicates.twicethe nucleus divides


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Meiosis: Two Part Cell DivisionMeiosis: Two Part Cell Division


HomologsHomologs

separateseparate

SisterSister

chromatidschromatids

separateseparate

DiploidDiploid

MeiosisMeiosis

II

MeiosisMeiosis

IIII

DiploidDiploid

HaploidHaploid


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Meiosis I

First division of meiosis


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Meiosis I: Reduction DivisionMeiosis I: Reduction Division


NucleusNucleus SpindleSpindle

fibersfibersNuclearNuclear

envelopeenvelopeEarly Prophase IEarly Prophase I

(Chromosome number(Chromosome numberdoubleddoubled))

Late Prophase ILate Prophase I Metaphase IMetaphase I

Anaphase IAnaphase ITelophaseTelophase II ((diploid)diploid)


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Synapsis & Crossing Over


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Second Division of Meiosis

Meiosis


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Meiosis II: ReducingMeiosis II: ReducingChromosome NumberChromosome Number


Prophase IIProphase II Metaphase IIMetaphase II

Anaphase IIAnaphase II

TelophaseTelophase IIII

44 Genetically DifferentGenetically Different

haploid cellshaploid cells


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Meiosis AnimationMeiosis Animation



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Results of MeiosisResults of Meiosis


GametesGametes (ovum(ovum & sperm) form& sperm) form

Four haploid cells with one copyFour haploid cells with one copy

of each chromosomeof each chromosome

One allele of each geneOne allele of each gene

Different combinations of allelesDifferent combinations of allelesfor different genes along thefor different genes along the

chromosomechromosome


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FertilizationFertilization Putting it all togetherPutting it all together


11nn ==2323

22n =n = 4646

cell cycle & division

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