Mitosis & the Mitosis & the Cell CycleCell Cycle

Cell Growth & Cell Growth & DevelopmentDevelopment

Are cells of organisms the same size? Are cells of organisms the same size? Do your cells get bigger as you grow, Do your cells get bigger as you grow, or do you just produce more cells?or do you just produce more cells?

When talking about Cell When talking about Cell SizeSize…… …… Smaller is Smaller is BetterBetter!!

The larger a cell becomes, the more The larger a cell becomes, the more demands the cell places on its DNA, demands the cell places on its DNA, and the harder it is to supply with and the harder it is to supply with nutrients. nutrients.

Cell DivisionCell Division

Before a cell becomes to large, a Before a cell becomes to large, a growing cell will divide.growing cell will divide.

Cell division is the process by which Cell division is the process by which a a SingleSingle cell divides into cell divides into 2 Daughter2 Daughter cells.cells.

Cell DivisionCell Division = the series of events = the series of events that cells go through as they grow that cells go through as they grow and divide.and divide.

WHAT TO COPYWHAT TO COPY

COPY THE NOTES IN COPY THE NOTES IN YELLOWYELLOW

ChromosomesChromosomes Chromosomes= are Chromosomes= are

composed of composed of DNADNA--Which carries the Which carries the cell’s coded genetic cell’s coded genetic information.information.

Humans have Humans have 4646 chromosomes(chromosomes(2323 pairspairs).).

The chromosomes The chromosomes consist of consist of twotwo identicalidentical sister sister chromatids.chromatids.

Two Major Types of Cell Two Major Types of Cell DivisionDivision

MitosisMitosis- Somatic - Somatic cells (Body Cells)cells (Body Cells) Diploid 2NDiploid 2N

MeiosisMeiosis- Sex cells/ - Sex cells/ GametesGametes Haploid 1NHaploid 1N

MitosisMitosis Mitosis is the process by which the Mitosis is the process by which the

geneticgenetic information is information is replicatedreplicated and and distributed to daughter cells.distributed to daughter cells.

22 diploid(2N) daughter cells are diploid(2N) daughter cells are produced from produced from 11 diploid (2N) parent cell. diploid (2N) parent cell.

The Daughter cells are genetically The Daughter cells are genetically identicalidentical to the parent cell. to the parent cell.

There are There are 44 major stages to mitosis, major stages to mitosis, PMAT. Mitosis does NOT include PMAT. Mitosis does NOT include interphase.interphase.

InterphaseInterphase

InterphaseInterphase= The cell spends most of = The cell spends most of its life here; not part of the actual its life here; not part of the actual reproduction. NOT PART OF reproduction. NOT PART OF MITOSIS.MITOSIS. Cell grows and replicates its DNA and Cell grows and replicates its DNA and

centrioles.centrioles. Nuclear membrane is visibleNuclear membrane is visible Nucleus, Nucleolus, and chromatin can Nucleus, Nucleolus, and chromatin can

be seen.be seen.

InterphaseInterphase

ProphaseProphase

ProphaseProphase: first : first phase of Mitosisphase of Mitosis Nuclear membrane Nuclear membrane

breaks downbreaks down Chromosomes Chromosomes

become become visiblevisible CentriolesCentrioles

separateseparate Spindle formsSpindle forms

MetaphaseMetaphase

MetaphaseMetaphase: : Second part of Second part of MitosisMitosis Chromosomes Chromosomes

attach to spindleattach to spindle Chromosomes Chromosomes line line

upup across the across the centercenter of the cell of the cell

AnaphaseAnaphase

AnaphaseAnaphase: Third : Third step in Mitosisstep in Mitosis The sister The sister

chromatids chromatids separate and separate and movemove apartapart

towards towards oppositeopposite poles.poles.

The chromatids are The chromatids are now called now called chromosomes.chromosomes.

TelophaseTelophase

TelophaseTelophase: Fourth : Fourth stage of Mitosisstage of Mitosis Chromosomes gather Chromosomes gather

at opposite ends of at opposite ends of the cellthe cell

The The nuclearnuclear membrane begins to membrane begins to form and enclose the form and enclose the chromosomeschromosomes

Cell membraneCell membrane begins to begins to movemove inwardsinwards

CytokinesisCytokinesis CytokinesisCytokinesis: Final : Final

stage in stage in cellular cellular divisiondivision

Not MitosisNot Mitosis Works with telophaseWorks with telophase

The cytoplasm The cytoplasm dividesdivides completely in half.completely in half.

22 daughter cells with daughter cells with identical genetic identical genetic information are information are produced.produced.

MEIOSIS MEIOSIS

Sex cells and gametesSex cells and gametes

MeiosisMeiosis is the process by is the process by which sex cells/ gametes are which sex cells/ gametes are produced. produced.

These sex cells are These sex cells are haploid haploid (1N). (1N).

Number of Chromosomes Number of Chromosomes

Human body cells have Human body cells have 46 46 chromosomeschromosomes

Human sex cells, sperm Human sex cells, sperm and eggs, have and eggs, have 2323 chromosomeschromosomes. .

Why should gametes have Why should gametes have only half the number of only half the number of

normal chromosomes??? normal chromosomes???

During meiosis, During meiosis, FOUR FOUR haploid daughter cells haploid daughter cells are produced from are produced from ONE ONE diploid parent cell. diploid parent cell.

During meiosis the cell During meiosis the cell actually divides actually divides TWICETWICE Meiosis I and Meiosis Meiosis I and Meiosis IIII

Meiosis I

Interphase I Prophase I Metaphase I Anaphase I

Cells undergo a round of DNA replication, forming duplicate Chromosomes.

Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.

Spindle fibers attach to the chromosomes.

The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Section 11-4

Figure 11-15 Meiosis

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MEIOSIS IMEIOSIS I

Prophase I: Prophase I: aa. Homologous chromosome pairs move . Homologous chromosome pairs move

together, to form a together, to form a tetradtetrad. This pairing is . This pairing is called SYNAPSIScalled SYNAPSIS

b.b. Nuclear membrane disappearsNuclear membrane disappears

c.c. Crossing-over may occur at the CHIASMATACrossing-over may occur at the CHIASMATA

Crossing over allows for the exchange of Crossing over allows for the exchange of genetic information between neighboring genetic information between neighboring homologous chromosomes homologous chromosomes

Meiosis I

Interphase I Prophase I Metaphase I Anaphase I

Cells undergo a round of DNA replication, forming duplicate Chromosomes.

Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.

Spindle fibers attach to the chromosomes.

The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Section 11-4

Figure 11-15 Meiosis

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Section 11-4

Crossing-Over

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Section 11-4

Crossing-Over

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Section 11-4

Crossing-Over

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MEIOSIS IMEIOSIS I

Metaphase I:Metaphase I:

a.a.Tetrads line up at the Tetrads line up at the Equator.Equator.

b. Homologous b. Homologous Chromosomes line up Chromosomes line up next to each othernext to each other

Meiosis I

Interphase I Prophase I Metaphase I Anaphase I

Cells undergo a round of DNA replication, forming duplicate Chromosomes.

Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.

Spindle fibers attach to the chromosomes.

The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Section 11-4

Figure 11-15 Meiosis

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MEIOSIS IMEIOSIS I

Anaphase I:Anaphase I:

a. a. ONEONE homologous homologous chromosome of each pair gets chromosome of each pair gets pulled to opposite poles.pulled to opposite poles.

b. The sister chromatids do b. The sister chromatids do not separate. It is still not separate. It is still DIPLOIDDIPLOID

Meiosis I

Interphase I Prophase I Metaphase I Anaphase I

Cells undergo a round of DNA replication, forming duplicate Chromosomes.

Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.

Spindle fibers attach to the chromosomes.

The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Section 11-4

Figure 11-15 Meiosis

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MEIOSIS IMEIOSIS I

Telophase I and Telophase I and Cytokinesis: Cytokinesis:

a.a. Cells separate; two new Cells separate; two new cells are formed that are cells are formed that are HAPLOID.HAPLOID.

b.b. Nuclear membrane Nuclear membrane REFORMS.REFORMS.

InterphaseInterphase

Interphase Interphase occurs occurs between meiosis I and between meiosis I and meiosis II to prepare the meiosis II to prepare the cell for division againcell for division again

NO DNA REPLICATION NO DNA REPLICATION HAPPENS!!HAPPENS!!

Prophase IIProphase II

Chromosomes come together Chromosomes come together Spindle fibers appearSpindle fibers appear

Metaphase IIMetaphase II

The chromosomes align along The chromosomes align along middle of the equator.middle of the equator.

Anaphase IIAnaphase II

the fibers pull the chromatids apart the fibers pull the chromatids apart and toward opposite ends of the and toward opposite ends of the cells. Called disjunctioncells. Called disjunction

Telophase IITelophase II

The chromatids arrive at the either The chromatids arrive at the either end of each cell and new nuclear end of each cell and new nuclear membranes form.membranes form.

CytokinesisCytokinesis

The rest of the cell continues to The rest of the cell continues to divide. Only when two, distinct cells divide. Only when two, distinct cells form will cytokinesis, the division of form will cytokinesis, the division of the cell's cytoplasm, be complete.the cell's cytoplasm, be complete.

Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Final Results of MeiosisFinal Results of Meiosis

4 haploid daughter cells which will develop 4 haploid daughter cells which will develop into sex cellsinto sex cells

Each daughter cell has half of the genetic Each daughter cell has half of the genetic information of a somatic cellinformation of a somatic cell 23 chromosomes for each sex cell23 chromosomes for each sex cell

NOTE:NOTE:

Males will create 4 sperm cells for every one cell Males will create 4 sperm cells for every one cell that goes through meiosisthat goes through meiosis

Females will create 4 egg cells, BUT 3 will turn Females will create 4 egg cells, BUT 3 will turn into non usabale polar bodies and 1 will mature into non usabale polar bodies and 1 will mature into an egg cell.into an egg cell.

Meiosis AnimationMeiosis Animation

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