Cell Division & Mitosis

Yay Getting closer and closer to the FUN stuff!!!

Cell DivisionCell Division

• What is cell division? What is cell division? – Process where a cell splits into 2 Process where a cell splits into 2

individual daughter cellsindividual daughter cells

• Why do we need cell division?Why do we need cell division?New cells are produced forNew cells are produced for growth growth andand to to

replace damaged or old cellsreplace damaged or old cells

• There are 2 major typesThere are 2 major types– Mitosis- division of the NUCLEUSMitosis- division of the NUCLEUS– Cytokinesis- division of the Cytokinesis- division of the

CYTOPLASMCYTOPLASM

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DNA ReplicationDNA ReplicationReplication = Replication =

COPYCOPYDNA must be DNA must be

copiedcopied or or replicatedreplicated before before cell division cell division

Each new cell will Each new cell will then have an then have an identical copy of identical copy of the DNAthe DNA

Original DNA Original DNA strandstrand

Two new, Two new, identical DNA identical DNA

strandsstrands

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Identical Daughter Identical Daughter CellsCells

Parent CellParent Cell

Two Two identical identical daughter daughter

cellscells

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ChromosomesChromosomes

• These are super These are super important little friendsimportant little friends

• Here are someHere are some defining defining characteristicscharacteristics– Made of Made of tightly coiledtightly coiled DNA DNA– Found in the NUCLEUSFound in the NUCLEUS– The number depends on The number depends on

the organism they live inthe organism they live in… … usually 10-50usually 10-50

– Humans have 46 Humans have 46 chromosomes in pairs (23 chromosomes in pairs (23 pairs)pairs)

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Chromosomes in Dividing Chromosomes in Dividing CellsCells

chromosomes are made of 2 chromatids that are held together by the centromere

Called Sister Called Sister ChromatidsChromatids

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Types of Cell Types of Cell ReproductionReproductionAsexual reproductionAsexual reproduction -1 cell -1 cell

dividing to make 2 new, dividing to make 2 new, identicalidentical daughter cells daughter cells

ex. Mitosis ex. Mitosis & Binary Fission& Binary Fission

Sexual reproduction- two cellsSexual reproduction- two cells (egg & sperm)(egg & sperm) making new cellmaking new cell (zygote)(zygote) that is NOT identical to that is NOT identical to the originalthe original

ex. Meiosisex. Meiosis

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Cell Division in Cell Division in ProkaryotesProkaryotesProkaryotes Prokaryotes

(bacteria) (bacteria) divide into 2 divide into 2

identical identical cells through cells through

binary binary fissionfission

Parent Parent cellcell

2 identical 2 identical daughterdaughter cellscells

ChromosoChromosome me

replicatesreplicates

Cell Cell splitssplits

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The cell cycleThe cell cycle• Cell Cycle- events cells go through as they

grow and divide• The cell cycle consists of five phases:The cell cycle consists of five phases:

– GG11 (Primary Growth Phase) (Primary Growth Phase)• Cell increases in sizeCell increases in size

– S Phase (Synthesis)S Phase (Synthesis)• Chromosomes are replicatedChromosomes are replicated

– GG22 (Second Growth Phase) (Second Growth Phase)• Organelles are producedOrganelles are produced

– M PhaseM Phase• MITOSISMITOSIS

– CytokinesisCytokinesis

These These three three phases are phases are known as known as InterphaseInterphase

Sketch me!!!Sketch me!!!

InterphaseInterphase• Not Not technically a part oftechnically a part of mitosis mitosis• Includes G1, S, and G2Includes G1, S, and G2• Organelles double in number to Organelles double in number to

prepare for divisionprepare for division

Mitosis- Division of the Mitosis- Division of the nucleusnucleus

• These are the phases These are the phases – ProphaseProphase– MetaphaseMetaphase– AnaphaseAnaphase– TelophaseTelophase

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Four Mitotic StagesFour Mitotic Stages

ProphaseProphaseMetaphaseMetaphaseAnaphaseAnaphaseTelophaseTelophase

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Prophase• Spindle fibers form• Centrioles move to

opposite poles• Chromosomes

become visible

Metaphase• Chromosomes line up at the EQUATOR

Anaphase

• Centromeres divide• Chromatids separate

and move to the opposite poles

Telophase

• Nuclear membrane forms around each of the chromosomes

• Chromosomes unwind

• Cytokinesis begins

Cytokinesis

• Cytoplasm divides and one cell becomes two individual cells.

The difference

ANIMALS PLANTS

Extra credit!Extra credit!Cleavage Furrow is formedCleavage Furrow is formed

Extra CreditExtra CreditCell Plate is formedCell Plate is formed

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CytokinesisCytokinesis

Cleavage Cleavage furrow in furrow in

animal cellanimal cell

Cell plate in Cell plate in plant cellplant cell

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Mitosis in Onion Root Mitosis in Onion Root TipsTips

Do you see any stages of mitosis?Do you see any stages of mitosis?

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KaryotypeKaryotypeA picture of the A picture of the

chromosomes chromosomes from a human from a human cell arranged in cell arranged in pairs by sizepairs by size

Remember this! Remember this! We’ll make one We’ll make one of these after of these after Christmas!Christmas!

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