cell cycle & cell division - buck mountain

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Cellular Cellular DivisionDivision

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Asexual Cell Reproduction “Chapter 17”

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General Outcomes•

In this unit you will…

•

Describe the processes of mitosis and meiosis.

•

Explain the basic rules and processes associated with transmission of genetic characteristics.

•

Explain classical genetics at a molecular level.

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Curriculum Outcomes

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Key Terms

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The Importance of Cell Division• Imagine what you would look like if you

peeled your back after a sun burn and new cells did not replace the dead skin cells.

• Without cell division scratches would never heal.

• If your red blood cells did not divide you would die.

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Questions• Questions 1-3 page 556

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Cell Cycle

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Cell Cycle

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Cell Cycle• Cells reproduce to make new cells. The

process for making new cells is called the cell cycle.

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• New cells are produced by the cell cycle.

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Principles of Mitosis

• Cell theory states that all living things are made up of one or more cells.

• Cells are formed from preexisting cells by cell division.

• Binary fission

–

is a form of asexual reproduction in which one cell divides into two equal cells.

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•Division involves two phases: division of nuclear material division of cytoplasm

•Mitosis

–

is a type of cell division in which daughter cells receive the same number of chromosomes as the parent cell.

•Cytokinesis

–

the division of

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Cell DivisionCell Division

All cells are derived fromAll cells are derived from prepre--existingexisting cellscellsNew cells are produced for New cells are produced for growthgrowth and to replaceand to replace damaged or damaged or old cellsold cellsDiffers inDiffers in prokaryotesprokaryotes (bacteria) (bacteria) andand eukaryoteseukaryotes (protists, fungi, (protists, fungi, plants, & animals)plants, & animals)

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Chromosome Structure•

Chromosomes contain both DNA and a number of proteins.

•

Combination of DNA and proteins is called chromatin.

•

As a cell moves through the cell cycle, chromosomes may either be uncondensed or condensed.

•

Uncondensed are long, thin strands that cannot be seen under a microscope.

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•Condensed can be seen under a microscope, can be unduplicated or duplicated.

•Duplicated –

the original is attached to its copy by a centromere. While attached the two chromosomes are called sister chromatids

(contain

identical genetic material)

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•

Unduplicated and Duplicated Chromosomes

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Keeping Cells IdenticalKeeping Cells Identical

TheThe

instructions for instructions for making cell partsmaking cell parts

are encoded in the are encoded in the DNADNA, so each new , so each new cell must get acell must get a

complete set of the complete set of the DNA moleculesDNA molecules

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DNA ReplicationDNA ReplicationDNA must be DNA must be copied orcopied orreplicated replicated before cell before cell divisiondivisionEach new cell Each new cell will then have anwill then have anidentical copyidentical copy of of the DNAthe DNA

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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ChromosomesChromosomes

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Prokaryotic ChromosomeProkaryotic Chromosome

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

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Eukaryotic ChromosomesEukaryotic ChromosomesAll All eukaryoticeukaryotic cells store genetic cells store genetic information in chromosomesinformation in chromosomesMost eukaryotes have between Most eukaryotes have between 10 and 10 and 50 chromosomes50 chromosomes in their body cellsin their body cellsHuman body cellsHuman body cells have have 4646 chromosomes chromosomes or 23 identical pairsor 23 identical pairs

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Eukaryotic ChromosomesEukaryotic ChromosomesEach chromosome is composed of a Each chromosome is composed of a single,single, tightly coiled DNAtightly coiled DNA moleculemoleculeChromosomes Chromosomes cancan’’t be seent be seen when when cells cells arenaren’’t dividingt dividing and are called and are called chromatinchromatin

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Compacting DNA into Compacting DNA into ChromosomesChromosomes

DNA is tightly coiled aroundproteins called histones

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Chromosomes in Dividing CellsChromosomes in Dividing Cells

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

Called Sister ChromatidsCalled Sister Chromatids

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KaryotypeKaryotypeA A picturepicture of the of the chromosomes from chromosomes from a human cell a human cell arranged in pairs by arranged in pairs by sizesizeFirst 22 pairs are First 22 pairs are called called autosomesautosomesLast pair are the Last pair are the sex chromosomessex chromosomesXXXX female or female or XYXYmalemale

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Boy or Girl?Boy or Girl?

Y Y --

ChromosomeChromosome

X X --


The Y Chromosome DecidesThe Y Chromosome Decides

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Cell ReproductionCell Reproduction

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Types of Cell ReproductionTypes of Cell ReproductionAsexual reproductionAsexual reproduction involves a involves a single cellsingle cell dividing to make dividing to make 2 new, 2 new, identical daughter cellsidentical daughter cellsMitosis & binary fission Mitosis & binary fission are are examples of asexual reproductionexamples of asexual reproductionSexual reproductionSexual reproduction involves two involves two cells (egg & sperm) joining to make a cells (egg & sperm) joining to make a new cell (zygote)new cell (zygote) that is that is NOT NOT identical to the original cellsidentical to the original cellsMeiosis Meiosis is an exampleis an example

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Cell Division in Cell Division in ProkaryotesProkaryotes

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Cell Division in ProkaryotesCell Division in ProkaryotesProkaryotes such as Prokaryotes such as bacteriabacteria divide into 2 divide into 2 identical cells by the identical cells by the process of process of binary binary fissionfissionSingle chromosome Single chromosome makes a copy of makes a copy of itselfitselfCell wall forms Cell wall forms between the between the chromosomes dividing chromosomes dividing the cellthe cell

Parent Parent cellcell

2 identical daughter cells2 identical daughter cells

Chromosome Chromosome relicatesrelicates

Cell splitsCell splits

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Prokaryotic Cell Prokaryotic Cell Undergoing Binary FissionUndergoing Binary Fission

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The Cell The Cell CycleCycle

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Five Phases of the Cell CycleFive Phases of the Cell Cycle

GG11 -- primary growth phaseprimary growth phaseS S –– synthesis; DNA replicatedsynthesis; DNA replicatedGG22 -- secondary growth phasesecondary growth phasecollectively these 3 stages are collectively these 3 stages are called interphasecalled interphase

M M -- mitosismitosisC C -- cytokinesiscytokinesis

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Cell CycleCell Cycle

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Interphase Interphase -- GG11 StageStage

11stst growth stagegrowth stage after cell after cell divisiondivisionCells Cells maturemature by making more by making more cytoplasm & organellescytoplasm & organellesCell carries on its Cell carries on its normal normal metabolic activitiesmetabolic activities

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Interphase Interphase –– S StageS StageSynthesisSynthesis stagestageDNADNA is copied or is copied or replicatedreplicated

Two Two identical identical copies copies of DNAof DNA

Original Original DNADNA

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Interphase Interphase –– GG22 StageStage

22ndnd GrowthGrowth StageStageOccurs Occurs after DNA has been copiedafter DNA has been copiedAll cell All cell structures needed for structures needed for divisiondivision are made (e.g. centrioles)are made (e.g. centrioles)Both Both organelles & proteinsorganelles & proteins are are synthesizedsynthesized

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WhatWhat’’s Happening in Interphase?s Happening in Interphase?

What the cell looks likeWhat the cell looks like

Animal Cell

What’s occurring

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Sketch the Cell CycleSketch the Cell Cycle

Daughter Daughter CellsCells

DNA CopiedDNA Copied

Cells Cells MatureMature

Cells prepare for Cells prepare for DivisionDivision

Cell Divides into Cell Divides into Identical cellsIdentical cells

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MitosisMitosis

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MitosisMitosisDivision of the Division of the nucleusnucleusAlso called Also called karyokinesiskaryokinesisOnly occurs in Only occurs in eukaryoteseukaryotesHas Has fourfour stagesstagesDoesnDoesn’’t occur in t occur in some cells such some cells such as as brain cellsbrain cells

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Four Mitotic StagesFour Mitotic Stages

ProProphasephaseMetaMetaphasephaseAnaAnaphasephaseTeloTelophasephase

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Early ProphaseEarly ProphaseChromatinChromatin in nucleus condenses to in nucleus condenses to form form visible chromosomesvisible chromosomesMitotic spindle Mitotic spindle forms from fibers in forms from fibers in cytoskeleton or cytoskeleton or centrioles (animal)centrioles (animal)

ChromosomesChromosomes

NucleolusNucleolus CytoplasmCytoplasm

Nuclear MembraneNuclear Membrane

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Late ProphaseLate ProphaseNuclear membrane & nucleolusNuclear membrane & nucleolus are are broken downbroken downChromosomesChromosomes continue condensing & continue condensing & are are clearly visibleclearly visibleSpindle fibers called Spindle fibers called kinetochoreskinetochoresattach to the centromereattach to the centromere of each of each chromosomechromosomeSpindleSpindle finishes forming between the finishes forming between the poles of the cellpoles of the cell

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Late ProphaseLate Prophase

Nucleus & Nucleolus have disintegratedNucleus & Nucleolus have disintegrated

Chromosomes Chromosomes

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Spindle Fiber attached to Spindle Fiber attached to ChromosomeChromosome

Kinetochore FiberKinetochore Fiber


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Review of ProphaseReview of Prophase

What the cell What the cell looks likelooks like

WhatWhat’’s happenings happening

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Spindle FibersSpindle FibersThe mitotic The mitotic spindlespindle form from the form from the microtubulesmicrotubules in plantsin plants and and centrioles centrioles in animal cellsin animal cellsPolar fibers Polar fibers extend from one pole of extend from one pole of the cell to the opposite polethe cell to the opposite poleKinetochore fibersKinetochore fibers extend from the extend from the pole to the centromere of the pole to the centromere of the chromosome to which they attachchromosome to which they attachAstersAsters are short fibers radiating are short fibers radiating from centriolesfrom centrioles

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Sketch The SpindleSketch The Spindle

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MetaphaseMetaphaseChromosomes, attached to the Chromosomes, attached to the kinetochore fiberskinetochore fibers, move to the center , move to the center of the cellof the cellChromosomes are now lined up at the Chromosomes are now lined up at the equatorequator

Pole of Pole of the Cellthe Cell

Equator of CellEquator of Cell

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MetaphaseMetaphase

Chromosomes Chromosomes lined at the lined at the EquatorEquator

Asters at Asters at the polesthe poles

Spindle Spindle FibersFibers

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MetaphaseMetaphase

AsterAster

Chromosomes at EquatorChromosomes at Equator

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Review of MetaphaseReview of Metaphase

What the cell looks What the cell looks likelike

WhatWhat’’s s occurringoccurring

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AnaphaseAnaphaseOccurs Occurs rapidlyrapidlySister Sister chromatidschromatids are are pulled apart to pulled apart to opposite polesopposite polesof the cell by of the cell by kinetochore kinetochore fibersfibers

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AnaphaseAnaphase

Sister Sister Chromatids Chromatids

being being separatedseparated

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Anaphase ReviewAnaphase Review

What the What the cell looks cell looks

likelike

WhatWhat’’s s occurringoccurring

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TelophaseTelophaseSister chromatids at Sister chromatids at opposite opposite polespolesSpindle Spindle disassemblesdisassemblesNuclear envelopeNuclear envelope forms around forms around each set of sister chromatidseach set of sister chromatidsNucleolusNucleolus reappearsreappearsCYTOKINESISCYTOKINESIS occursoccursChromosomes reappear as Chromosomes reappear as chromatinchromatin

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Comparison of Anaphase & TelophaseComparison of Anaphase & Telophase

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CytokinesisCytokinesisMeans division of the cytoplasmMeans division of the cytoplasmDivisionDivision of cell into two, of cell into two, identical halves called identical halves called daughter daughter cellscellsIn plant cells, cell plate In plant cells, cell plate forms forms at the equator to divide cellat the equator to divide cellIn animal cells, In animal cells, cleavage furrow cleavage furrow forms to split cellforms to split cell

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CytokinesisCytokinesis

Cleavage furrow Cleavage furrow in animal cellin animal cell

Cell plate in Cell plate in plant cellplant cell

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Mitotic StagesMitotic Stages

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Daughter Cells of MitosisDaughter Cells of MitosisHave the Have the same number of same number of chromosomes as each otherchromosomes as each other and as and as the parent cellthe parent cell from which they from which they were formedwere formedIdenticalIdentical to each other, but to each other, but smaller smaller than parent cellthan parent cellMust Must grow in sizegrow in size to become mature to become mature cells cells (G(G11 of Interphase)of Interphase)

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Identical Daughter CellsIdentical Daughter Cells

Chromosome number the Chromosome number the samesame, but cells , but cells smallersmaller

than parent cellthan parent cell

What is What is the 2n the 2n

or or diploid diploid

number?number?22

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Review Review of of

MitosisMitosis

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InterphaseInterphase

ProphaseProphase

MetaphaseMetaphaseAnaphaseAnaphase

TelophaseTelophase

Name the Mitotic Stages:Name the Mitotic Stages:

Name this?Name this?

Name this?Name this?

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Eukaryotic Cell DivisionEukaryotic Cell Division

Used for Used for growth and growth and repairrepairProduce two new cells Produce two new cells identical to the original identical to the original cellcellCells are Cells are diploid (2n)diploid (2n)

Chromosomes during Chromosomes during Metaphase of mitosisMetaphase of mitosis

ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophaseCytokinesisCytokinesis

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Mitosis AnimationMitosis AnimationName each stage as you see it occur?Name each stage as you see it occur?

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Mitosis in Onion Root TipsMitosis in Onion Root TipsDo you see any stages of mitosis?Do you see any stages of mitosis?

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Draw & Learn these StagesDraw & Learn these Stages

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Draw & Learn these StagesDraw & Learn these Stages

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Test Yourself Test Yourself over Mitosisover Mitosis

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Mitosis QuizMitosis Quiz

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Mitosis QuizMitosis Quiz

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Name the Stages of Mitosis:Name the Stages of Mitosis:

Interphase

Early prophase

Mid-ProphaseLate Prophase

Metaphase

Late Anaphase

Early Anaphase

Early Telophase,

Begin cytokinesis

Late telophase, Advanced cytokinesis

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Identify the StagesIdentify the Stages

Early, Middle, & Late Prophase Early, Middle, & Late Prophase

Late ProphaseLate Prophase MetaphaseMetaphase AnaphaseAnaphase

Late AnaphaseLate Anaphase TelophaseTelophase Telophase & Telophase & CytokinesisCytokinesis

??

?? ?? ??

?? ?? ??

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Locate the Four Mitotic Locate the Four Mitotic Stages in PlantsStages in Plants

MetaphaseMetaphase

ProphaseProphase

AnaphaseAnaphase

TelophaseTelophase

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Uncontrolled MitosisIf mitosis is not If mitosis is not controlledcontrolled, unlimited , unlimited cell division occurs cell division occurs causing cancerous causing cancerous tumorstumorsOncogenesOncogenes are special are special proteins proteins that increase the chance increase the chance that a normal that a normal cell cell develops into adevelops into a tumor tumor cell cell

Cancer cellsCancer cells

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Quick Review…

•Quick Review…

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Stages of Cell Division “Interphase”•

Interphase

–

describes the processes of cell activity

between divisions.

•

Most cells spend their time in this phase.

•

Cell grows, and carries out chemical activities that sustain life during this period.

•

Cells make proteins to repair damage, move nutrients.

•

Single strands become double strands.

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“Prophase”•

First phase of cell division.

•

Contents of nucleus become visible (chromosomes shorten + thicken)

•

Centrioles

-

Small bodies that separate and move to

opposite poles. (provide attachment for spindle fibers)

•

Spindle fibers

–

are protein structures that guide

chromosomes during cell division.

•

Chromosomes consist of two chromatids

held together by

a centromere.

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“Metaphase”•

Second phase

•

Chromosomes composed of sister chromatids

move

toward the center of the cell.

•

This area is called the equatorial plate (imaginary line that divides the cell and its chromosomes)

•

Chromosomes appear are dark thick masses attached to spindle fibers.

•

Chromatids

become intertwined.

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“Anaphase”• Third phase

• Centromeres

divide and chromatids

move to opposite poles of the cell.

• Same number of single-stranded chromosomes will be found at each pole.

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“Telophase”•

Last phase

•

Chromosomes reach opposite poles of the cell

•

They begin to lengthen and intertwine.

•

Spindle fibers dissolve and nuclear membrane begins to form around each mass of chromatin.

•

Telophase

is followed by the division of the cyctoplasm.

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“Cytoplasm Division”•

Once chromosomes have moved to opposite poles, the cytoplasm begins to divide.

•

Cytokinesis

–

or division of the cytoplasm, appears to be separate from nuclear division.

•

Division of the cytoplasm must provide organelles for each newly established cell.

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Mitosis

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Mitosis

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Summary

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QUIZ

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Identify the stage of the cell cycle.

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Homework• Review Questions (old text)• Page 434 Questions 1 -

6

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Cloning• Process of forming identical offspring from

a single cell or tissue in the parent organ.

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Plant Cloning

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Plant Cloning Technology• 1958 Fredrick Stewart revealed that he had

produced a plant from a single carrot cell.

• Many plants like orchids are produced from clones

• Not all plants can be cloned grass and legume families cannot.

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Lab

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Plant Cloning

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Animal Cloning Technology•

Robert Biggs and Thomas King investigated nuclear transplants in frogs.

•

Extracted nucleus from an unfertilized egg with a glass tube.

•

The egg cell with the transplanted nucleus began to divide.

•

Dolly the sheep was another example of this

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Animal Cloning

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Animal Cloning

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Animal Cloning

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Dolly

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Summary

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Homework• Review Questions (old text)• Page 440 Questions 7 -12 • Page 443 Questions 13 -17

• Questions 1-4 page 569• Questions 1-7 page 571

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MeiosisMeiosis Formation of GametesFormation of Gametes (Eggs & Sperm)(Eggs & Sperm)

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Facts About MeiosisFacts About MeiosisPreceded by interphase which Preceded by interphase which includesincludes chromosome replicationchromosome replicationTwoTwo meiotic divisions meiotic divisions ------ Meiosis Meiosis I and Meiosis III and Meiosis IICalled ReductionCalled Reduction-- divisiondivisionOriginal cell is diploid (2n)Original cell is diploid (2n)Four daughter cellsFour daughter cells produced that produced that are are monoploid (1n)monoploid (1n)

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Facts About MeiosisFacts About MeiosisDaughter cellsDaughter cells contain half the contain half the number of chromosomesnumber of chromosomes as the as the original celloriginal cellProducesProduces gametesgametes (eggs & sperm(eggs & sperm))Occurs in the Occurs in the testestestes in males in males ((SpermatogenesisSpermatogenesis))Occurs in the Occurs in the ovariesovaries in females in females ((OogenesisOogenesis))

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Start with Start with 46 double stranded 46 double stranded chromosomes (2n)chromosomes (2n)After 1 division After 1 division -- 23 double 23 double

stranded chromosomes (n)stranded chromosomes (n)After 2nd division After 2nd division -- 23 single 23 single

stranded chromosomes (n)stranded chromosomes (n)Occurs in our Occurs in our germ cellsgerm cells that that

produce gametesproduce gametes

More Meiosis FactsMore Meiosis Facts

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Why Do we Need Meiosis?Why Do we Need Meiosis?It is the fundamental basis of It is the fundamental basis of sexual reproductionsexual reproductionTwo haploid (1n) gametes are Two haploid (1n) gametes are brought together through brought together through fertilizationfertilization to form a diploid to form a diploid (2n) zygote(2n) zygote

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Fertilization Fertilization –– ““Putting it Putting it

all togetherall together””

1n =31n =3

2n = 62n = 6

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Replication of ChromosomesReplication of ChromosomesReplicationReplication is the is the process of process of duplicating a duplicating a chromosomechromosomeOccurs Occurs prior to prior to divisiondivisionReplicated copies Replicated copies are called are called sister sister chromatidschromatidsHeld together at Held together at centromerecentromere

Occurs in Occurs in InterphaseInterphase

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A Replicated ChromosomeA Replicated Chromosome

HomologsHomologs(same genes, (same genes,

different alleles)different alleles)

SisterSister ChromatidsChromatids

(same genes,(same genes,same alleles)same alleles)

Gene XGene X

Homologs separate in meiosis I and Homologs separate in meiosis I and therefore different alleles separate.therefore different alleles separate.

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Meiosis Forms Haploid GametesMeiosis Forms Haploid GametesMeiosis must Meiosis must reduce the chromosome number reduce the chromosome number by halfby halfFertilization then restoresFertilization then restores the 2n numberthe 2n number

from mom from dad child

meiosis reducesgenetic content

toomuch!

The right number!

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Meiosis: Two Part Cell Meiosis: Two Part Cell DivisionDivision

HomologsHomologsseparateseparate

Sister Sister chromatidschromatidsseparateseparate

DiploidDiploid

MeiosisMeiosis II

MeiosisMeiosis IIII

DiploidDiploid

HaploidHaploid

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Meiosis I: Reduction DivisionMeiosis I: Reduction Division

NucleusNucleus SpindleSpindlefibersfibers NuclearNuclear

envelopeenvelopeEarly Early Prophase IProphase I

(Chromosome (Chromosome number number doubleddoubled))

Late Late Prophase Prophase

II

Metaphase Metaphase II Anaphase Anaphase

IITelophase I Telophase I

(diploid)(diploid)

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Prophase IProphase I

Early prophaseEarly prophaseHomologs pair.Homologs pair.Crossing over Crossing over

occursoccurs.

Late prophaseLate prophaseChromosomes condense.Chromosomes condense.Spindle forms.Spindle forms.Nuclear envelope Nuclear envelope

fragments.fragments.

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Tetrads Form in Prophase ITetrads Form in Prophase I

Homologous chromosomesHomologous chromosomes (each with sister (each with sister

chromatids) chromatids)

Join to form aJoin to form a TETRADTETRAD

Called SynapsisCalled Synapsis

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CrossingCrossing--OverOverHomologous Homologous chromosomeschromosomes in in a tetrad a tetrad cross cross over each otherover each otherPieces of Pieces of chromosomes or chromosomes or genes are genes are exchangedexchangedProduces Produces Genetic Genetic recombinationrecombination in in the offspringthe offspring

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Homologous Chromosomes Homologous Chromosomes During CrossingDuring Crossing--OverOver

129

CrossingCrossing--over multiplies the already huge over multiplies the already huge number of different gamete types number of different gamete types

produced by independent assortmentproduced by independent assortment

CrossingCrossing--OverOver

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Metaphase IMetaphase I

Homologous pairsHomologous pairs of chromosomes of chromosomes

align along the align along the equatorequator

of the of the

cellcell

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Anaphase IAnaphase I

Homologs separateHomologs separate

and and move to opposite poles.move to opposite poles.

Sister chromatids Sister chromatids remain remain attached attached at theirat their

centromerescentromeres.

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Telophase ITelophase I

Nuclear envelopes Nuclear envelopes reassemble.reassemble.

Spindle disappears.Spindle disappears.

Cytokinesis Cytokinesis divides cell divides cell into two.into two.

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Meiosis IIMeiosis IIOnly one homolog of each Only one homolog of each

chromosome is present in chromosome is present in the cellthe cell.

Meiosis II produces gametes with Meiosis II produces gametes with one copy of each chromosome and one copy of each chromosome and thus one copy of each gene.thus one copy of each gene.

Sister chromatids carry Sister chromatids carry identical genetic identical genetic informationinformation. .

Gene XGene X

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Meiosis II: Reducing Meiosis II: Reducing Chromosome NumberChromosome Number

Prophase Prophase IIII Metaphase Metaphase

IIIIAnaphase Anaphase

IIII

Telophase Telophase IIII 4 Identical 4 Identical

haploid cellshaploid cells

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Prophase IIProphase II

Nuclear envelope Nuclear envelope fragments.fragments.

Spindle forms.Spindle forms.

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Metaphase IIMetaphase II

Chromosomes align Chromosomes align along along equatorequator of cellof cell..

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Anaphase IIAnaphase II

Sister chromatidsSister chromatids separate and separate and

move to move to opposite opposite polespoles.

EquatorEquator

PolePole

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Telophase IITelophase II

Nuclear envelope Nuclear envelope assembles.assembles.

Chromosomes Chromosomes decondense.decondense.

Spindle disappears.Spindle disappears.

Cytokinesis divides Cytokinesis divides cell into two.cell into two.

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Results of MeiosisResults of MeiosisGametes (egg & sperm) Gametes (egg & sperm) formform

Four haploid cells with Four haploid cells with one copy of each one copy of each chromosome chromosome

One allele of each geneOne allele of each gene

Different combinations Different combinations of alleles for different of alleles for different genes along the genes along the chromosomechromosome

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GametogenesisGametogenesisOogenesisOogenesis

oror SpermatogenesisSpermatogenesis

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SpermatogenesisSpermatogenesisOccurs in the Occurs in the testestestesTwo divisions Two divisions produce 4 produce 4 spermatidsspermatidsSpermatids Spermatids mature mature into sperminto spermMen produce about Men produce about 250,000,000 250,000,000 sperm per daysperm per day

143

Spermatogenesis in the Spermatogenesis in the TestesTestes

SpermatidSpermatid

144

SpermatogenesisSpermatogenesis

145

OogenesisOogenesisOccurs in the Occurs in the ovariesovariesTwo divisions produce Two divisions produce 3 polar bodies3 polar bodiesthat die and that die and 1 egg1 eggPolar bodies die because of Polar bodies die because of unequal unequal division of cytoplasmdivision of cytoplasmImmature egg called Immature egg called oocyteoocyteStarting at puberty, one oocyte Starting at puberty, one oocyte matures into an matures into an ovum (egg)ovum (egg) every 28 every 28 daysdays

146

Oogenesis in the OvariesOogenesis in the Ovaries

147

OogenesisOogenesis

OogoniumOogonium(diploid)(diploid)

MitosisMitosis

PrimaryPrimaryoocyteoocyte(diploid)(diploid)

Meiosis IMeiosis I

SecondarySecondaryoocyteoocyte(haploid)(haploid)

Meiosis IIMeiosis II(if fertilization(if fertilizationoccurs)occurs)

First polar bodyFirst polar bodymay divide may divide (haploid)(haploid) PolarPolar

bodiesbodiesdiedie

Ovum (egg)Ovum (egg)

SecondSecondpolar bodypolar body(haploid)(haploid)

a

A

X

X

a

X

A X

a

X

a

X

MatureMatureeggegg

A

X

A

X

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Comparing Comparing Mitosis and Mitosis and

MeiosisMeiosis

149

MitosisMitosis MeiosisMeiosisNumber of Number of

divisionsdivisions 1122

Number of Number of daughter cellsdaughter cells 22 44

Genetically Genetically identical?identical? YesYes NoNo

Chromosome #Chromosome # Same as parentSame as parent Half of parentHalf of parent

WhereWhere Somatic cellsSomatic cells Germ cellsGerm cells

WhenWhen Throughout lifeThroughout life At sexual maturityAt sexual maturity

RoleRole Growth and Growth and repairrepair Sexual reproductionSexual reproduction

Comparison of DivisionsComparison of Divisions

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Karyotype Charts• Page 584 –

585 exercise

• Questions 1-

6 page 586

• Review page 592 -

595

cell cycle & cell division - buck mountain

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