MitosisMitosis

Why Mitosis?Why Mitosis?

The purpose of mitosis is to The purpose of mitosis is to generate two new cells from one generate two new cells from one cell.cell. The “daughter cells” generated are The “daughter cells” generated are

exact copies of the “parent cell”exact copies of the “parent cell” Mitosis is happening in many cells Mitosis is happening in many cells

in your body as we speak!in your body as we speak! Some cells divide more frequently Some cells divide more frequently

than othersthan others

Mitosis is part of the Mitosis is part of the Cell CycleCell Cycle

Interphase

Mitosis

Cytokinesis

Key Events in the Cell Key Events in the Cell CycleCycle

The cell gets largerThe cell gets larger

Organelles are madeOrganelles are made

Genetic information is duplicatedGenetic information is duplicated

Half of the DNA and organelles go to Half of the DNA and organelles go to one end and the other half to the one end and the other half to the opposite endopposite end

The cell is split down the middle to The cell is split down the middle to make 2 new cellsmake 2 new cells

Interphase

InterphaseInterphase

Gap1 (G1)Gap1 (G1) Preparation for growthPreparation for growth Organelles, membranes, and ribosomes Organelles, membranes, and ribosomes

mademade

Synthesis (S)Synthesis (S) Chromosomes replicatedChromosomes replicated

Gap2 (G2)Gap2 (G2) Preparation for divisionPreparation for division Mitochondria divideMitochondria divide

Remember, mitochondria have their own Remember, mitochondria have their own chromosome!chromosome!

Mitosis

Cytokinesis

G1

G2

S

Q4 Part 1

Key Events in the Cell Key Events in the Cell CycleCycle

The cell gets largerThe cell gets larger

Organelles are madeOrganelles are made

Genetic information is duplicatedGenetic information is duplicated

Half of the DNA and organelles go to Half of the DNA and organelles go to one end and the other half to the one end and the other half to the opposite endopposite end

The cell is split down the middle to The cell is split down the middle to make 2 new cellsmake 2 new cells

Interphase

MitosisQ7

Chromosomes in Somatic Chromosomes in Somatic CellsCells

Nucleus of cell during G1 Chromosomes not duplicated

Nucleus of cell after S phase Chromosomes are duplicated

Nucleus of cell after mitosis Chromosomes are not duplicated

Homologous pair

Keep in Mind…Keep in Mind…

MitosisMitosis

ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

Interphase

A

Cytokinesis

PM

T

ProphaseProphase

Pro =forward, forthPro =forward, forth Chromosomes condenseChromosomes condense Nuclear envelope breaks downNuclear envelope breaks down

Membrane surrounding the nucleusMembrane surrounding the nucleus

Centrioles move to opposite polesCentrioles move to opposite poles Spindle fibers growSpindle fibers grow

Q4 Part 2

MetaphaseMetaphase

Meta =after, withMeta =after, with Chromosomes line up at the midlineChromosomes line up at the midline Spindle attaches to chromosomes at the Spindle attaches to chromosomes at the

centromerecentromere The centromere is where the sister The centromere is where the sister

chromatids are attachedchromatids are attached

Q4 Part 2

AnaphaseAnaphase

Ana =againstAna =against Centromeres splitCentromeres split Sister chromatids are pulled to opposite Sister chromatids are pulled to opposite

poles by the shortening of spindle fiberspoles by the shortening of spindle fibers Once separated, each sister chromatid is Once separated, each sister chromatid is

now a chromosome (and each is exactly like now a chromosome (and each is exactly like the chromosome found in the original cell the chromosome found in the original cell before S of interphase)before S of interphase)

Q4 Part 2

TelophaseTelophase

Telo =completion of a goalTelo =completion of a goal Spindle breaks downSpindle breaks down Nuclear envelope forms in each Nuclear envelope forms in each

of the daughter cellsof the daughter cells Chromosomes decondenseChromosomes decondense

Q4 Part 2

Key Events in the Cell Key Events in the Cell CycleCycle

The cell gets largerThe cell gets larger

Organelles are madeOrganelles are made

Genetic information is duplicatedGenetic information is duplicated

Half of the DNA and organelles go to Half of the DNA and organelles go to one end and the other half to the one end and the other half to the opposite endopposite end

The cell is split down the middle to The cell is split down the middle to make 2 new cellsmake 2 new cells

Interphase

MitosisQ7

Cytokinesis

CytokinesisCytokinesis

““Cell-making” phaseCell-making” phase Organelles and Organelles and

cytoplasm are cytoplasm are distributed between distributed between daughter cellsdaughter cells

Microfilament band at Microfilament band at equator contracts to equator contracts to pinch apart 2 new pinch apart 2 new daughter cellsdaughter cells

Interphase

Cytokinesis

Mitosis

Summary of Cell CycleSummary of Cell Cycle

Cell growsCell grows DNA replicatesDNA replicates Organelles are madeOrganelles are made Chromosomes condenseChromosomes condense Chromosomes line up at the equatorChromosomes line up at the equator Replicated chromosomes are pulled Replicated chromosomes are pulled

apart to opposite polesapart to opposite poles Chromosomes decondenseChromosomes decondense Two daughter cells are formedTwo daughter cells are formed

G1

S

G2

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

I

A

C

PM

T

I Pee on the

MAT, See?

GGoo

Resting phaseResting phase Cell may:Cell may:

Enter S phaseEnter S phase DieDie

Cell is damaged Cell is damaged

Do nothingDo nothing NeuronNeuron

GoCell Death

Sit tight

Mitosis

Cytokinesis

G1

G2

S

Cell Cycle CheckpointsCell Cycle Checkpoints

Mitosis

Cytokinesis

G1

G2

S

DNA damage checkpoints

Spindle checkpoint

ApoptosisApoptosis

Programmed cell deathProgrammed cell death Neat and orderlyNeat and orderly

NecrosisNecrosis

Cell explodesCell explodes Not so neat and orderlyNot so neat and orderly

In response to injuryIn response to injury

TelomeresTelomeres

Consist of a repeated sequence Consist of a repeated sequence of DNAof DNA Nature’s solution to the end-replication problemNature’s solution to the end-replication problem

Very tips of chromosomes cannot be replicatedVery tips of chromosomes cannot be replicated Shortened with each mitotic divisionShortened with each mitotic division Limits # of possible cell divisionsLimits # of possible cell divisions Cell will not divide after ~50 divisionsCell will not divide after ~50 divisions Not found in eggs/sperm, bone marrow cells, cancer Not found in eggs/sperm, bone marrow cells, cancer

cellscells Shortening is hastened by chronic stressShortening is hastened by chronic stress

Cell DifferentiationCell Differentiation

The process whereby a cell becomes specializedThe process whereby a cell becomes specialized Every cell contains the exact same genetic Every cell contains the exact same genetic

information (all 23 chromosome pairs)information (all 23 chromosome pairs) One chromosome from mom and one from dadOne chromosome from mom and one from dad

Not all genetic info is being used by every cellNot all genetic info is being used by every cell Different cell types are making Different cell types are making

different proteinsdifferent proteins

The proteins being made by a cell The proteins being made by a cell

give it specialized characteristics give it specialized characteristics

((e.g. e.g. blood cell vs. brain cell) blood cell vs. brain cell)

Stem CellsStem Cells

Important for regenerating cells that are lost (Important for regenerating cells that are lost (e.g.e.g. skin skin cells) and for growthcells) and for growth

Stem cells are undifferentiatedStem cells are undifferentiated Totipotent =able give rise to any cell typeTotipotent =able give rise to any cell type

Progenitor cellsProgenitor cells Somewhat specializedSomewhat specialized Pluripotent =able to produce manyPluripotent =able to produce many different cell typesdifferent cell types

Pathways to Cell Pathways to Cell SpecializationSpecialization

Each specialized Each specialized cell type uses cell type uses only certain only certain “recipes” from “recipes” from the “cookbook”the “cookbook”

Embryonic Stem Cells -Embryonic Stem Cells -IVFIVF

Yields totipotent cellsYields totipotent cells Uses frozen embryos from Uses frozen embryos from in vitroin vitro

fertilizationfertilization in vitro in vitro =in a dish=in a dish in vivoin vivo =in the body =in the body

Embryonic Stem Cells –Embryonic Stem Cells –Nuclear TransfectionNuclear Transfection

CloningCloning

Adult Stem CellsAdult Stem Cells

Pluripotent Pluripotent Found in bone marrow, Found in bone marrow,

umbilical cord blood, umbilical cord blood, certain parts of the braincertain parts of the brain

Even I have stem

cells!