Cell Cycle & Mitosis

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Cell DivisionCell DivisionAll cells are derived fromAll cells are derived from

pre-existingpre-existing cellscells

New cells are produced for New cells are produced for growthgrowth and to replace and to replace damaged or old cellsdamaged or old cells

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Keeping Cells IdenticalKeeping Cells Identical

TheThe instructions instructions for making cell for making cell partsparts are encoded are encoded in the in the DNADNA, so , so each new cell each new cell must get amust get a complete set of complete set of the DNA the DNA moleculesmolecules

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DNA ReplicationDNA ReplicationDNA must be DNA must be

copied orcopied or replicated replicated before cell before cell divisiondivision

Each new cell Each new cell will then have will then have anan identical identical copycopy of the of the DNADNA

Original DNA Original DNA strandstrand

Two new, Two new, identical DNA identical DNA strandsstrands

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Identical Daughter CellsIdentical Daughter Cells

Parent CellParent Cell

Two Two identical identical daughter daughter cellscells

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Prokaryotic ChromosomeProkaryotic Chromosome

The DNA of The DNA of prokaryotes prokaryotes (bacteria) is (bacteria) is one, circular one, circular chromosomechromosome attached to attached to the inside of the inside of the cell the cell membranemembrane

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Eukaryotic Eukaryotic ChromosomesChromosomesEach chromosome is composed Each chromosome is composed

of a of a single,single, tightly coiled DNAtightly coiled DNA moleculemolecule

Chromosomes Chromosomes cancan’’t be seent be seen when cells when cells aren‘t dividingaren‘t dividing  and and are called are called chromatinchromatin

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Eukaryotic Eukaryotic ChromosomesChromosomes

All All eukaryoticeukaryotic cells store cells store genetic information in genetic information in chromosomeschromosomes

Most eukaryotes have between Most eukaryotes have between 10 10 and 50 chromosomesand 50 chromosomes in their body in their body cellscells

Human body cellsHuman body cells have have 4646 chromosomes or 23 identical pairschromosomes or 23 identical pairs

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Chromosomes in Dividing Chromosomes in Dividing CellsCells

Duplicated chromosomes are called chromatids & are held together by the centromere

Called Sister Called Sister ChromatidsChromatids

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KaryotypeKaryotypeA A picturepicture of the of the

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

First 22 pairs are First 22 pairs are called called autosomesautosomes

Last pair are the Last pair are the sex chromosomessex chromosomes

XXXX female or female or XYXY malemale

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Boy or Girl?Boy or Girl?

Y - Y - ChromosomeChromosome

X - X - ChromosomeChromosome

The Y Chromosome The Y Chromosome DecidesDecides

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The Cell CycleThe Cell Cycle

Interphase = between phases

Chromatin

DNA Duplicates

G1First growth phase

- Cell grows in size-Creates mRNA and proteins-Ends when the cell enters into the S phase

S PHASE

DNA is Replicated

S phase occurs between G1 and G2

G2

Cell continues to grow and create mRNA and proteins

Cell will duplicate organelles getting ready for the Mitosis phase

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MitosisMitosisDivision of the Division of the

nucleusnucleusOnly occurs in Only occurs in

eukaryoteseukaryotesHas Has fourfour

stagesstagesDoesnDoesn’’t occur t occur

in some cells in some cells such as such as brain brain cellscells

Mitosis = New CellsResults in 2 identical daughter cells

4 chromosomes 4 chromosomes

Onion Root Tip Mitosis Pictures

Interphase

Prophase

Chromosomes (and copies) condense

Chromatid = copy

Nuclear Membrane dissappears

Centriole spindles form

Prophase

Metaphase

Nuclear Membrane

gone

Centrioles Move

Spindles grow

Chromosomes (with copies)

line up

Metaphase

Nuclear Membrane

gone

Centrioles Move

Spindles grow

Chromosomes (with copies)

line up

Metaphase

Anaphase

Spindles contract

Copies pulled apart

Anaphase

Spindles contract

Copies pulled apart

Anaphase

Early Telophase

Spindles gone

Nuclear Membranes

form

Early Telophase

Late TelophaseNuclear

Membranes are complete

Mitosis is complete.

Late Telophase

CytokinesisCell splits

Cytokinesis

Quiz

Metaphase

Interphase = between phases

Chromatin

DNA Duplicates

Metaphase

Prophase

Anaphase

Telophase

Late TelophaseNuclear

Membranes are complete

Mitosis is complete.

Mitosis = New CellsResults in 2 identical daughter cells

4 chromosomes 4 chromosomes