THE CELL CYCLE THE CELL CYCLE IPMAT Regulation & IPMAT Regulation & Its Lifespan Its Lifespan Implication Implication
Dec 31, 2015
THE CELL CYCLETHE CELL CYCLE
IPMAT Regulation & IPMAT Regulation &
Its Lifespan ImplicationIts Lifespan Implication
Why Do Cells Divide?Why Do Cells Divide?
Why Do Cells Divide?Why Do Cells Divide?
ReproductionReproduction– Binary Fission in bacteria
Tissue GrowthTissue Growth– Growth in multicellular organisms = more
cells not larger cells Tissue RepairTissue Repair Maintain High Surface Area:VolumeMaintain High Surface Area:Volume
– High volume = low efficiency
Parts in the Process:Parts in the Process: ChromosomesChromosomes
http://anatomy.iupui.edu/courses/histo_D502/D502f04/lecture.f04/cell.f04/cellf04.html http://mbbnet.umn.edu/icons/chromosome.jpeg
Parts in the Process:Parts in the Process: Centrioles & The MTOCCentrioles & The MTOC
http://sparkleberrysprings.com/v-web/b2/images/lotc/centriole14.jpg
Parts in the Process:Parts in the Process: Spindle Fibers & KinetochoresSpindle Fibers & Kinetochores
http://www.nikonsmallworld.com/gallery.php?grouping=year&year=2004&imagepos=18
Parts in the ProcessParts in the Process CentriolesCentrioles
– animal cells only– MT– spindle fiber organization
Centrosomes Centrosomes – plant & animal cells– AKA MTOC’s
www.cellsalive.com
http://osumolgen.siteturbine.com/sites/osumolgen/images/met3.jpg
Parts in the ProcessParts in the Process
ChromosomesChromosomes– Super-coiled DNA – centromeres
Spindle FibersSpindle Fibers– MT’s attached to centromeres @
kinetochore– Tracks for chromosome movement toward
centrioles @ poles
http://www2.geneticsolutions.com/PageReq?id=3844:1873
http://www2.geneticsolutions.com/PageReq?id=3844:1873
The Cell CycleThe Cell Cycle
IInterphase can be divided into 3 main substages: – GG11 – Gap 1 - period of growth
– SS – Synthesis – DNA is copied (synthesized)
– GG22 – Gap 2 – preparation for division
The Cell CycleThe Cell Cycle (continued) Following GG22 of IInterphase, mitosis
(M-phase) carries out division:– PProphase– MMetaphase– AAnaphase – TTelophase & Cytokinesis http://www.biology.iupui.edu/biocourses/
N100/2k4ch8mitosisnotes.html
ProphaseProphase Centrosomes to poles Nuclear membrane disappears Chromatin condenses to form
chromosomes
http://micro.magnet.fsu.edu/micro/gallery/mitosis/lateprophase.html http://www.dundee.ac.uk/biocentre/GRE%20Scientific%20images/pages/Prophase.htm
MetaphaseMetaphase Chromosomes in middle of cell Spindle fibers form Kinetochores attach to centromeres of
each chromatid
http://www.brown.edu/Courses/BI0020_Miller/images/metaphase-1.jpg http://www.pc.vccs.edu/biology-labmanual/lab7mitmei/whitefishmeta.jpg
AnaphaseAnaphase Sister chromatids separate Chromatids move to poles using
retreating spindle fibers (D.I.)
http://micro.magnet.fsu.edu/micro/gallery/mitosis/earlyanaphase.html http://content.answers.com/main/content/wp/en/thumb/3/38/300px-Anaphase-flourescent.jpg
Telophase & CytokinesisTelophase & Cytokinesis TelophaseTelophase complete division of nucleus
– Spindle fibers disappear– Nuclear membranes reappear
CytokinesisCytokinesis complete division of cytoplasm– Cleavage furrow in animals– Cell plate in plants
http://iknow.net/CDROMs/cell_cdrom/index.html
Plant Animation
Animal Mitosis
http://www.cbp.pitt.edu/faculty/yong_wan/index.html
Asymmetric DivisionAsymmetric Division Specialization of stem cells New daughter cells not identical
http://labshelf.com/stem-cells-treatments-research.html http://labshelf.com/stem-cells-treatments-research.html
Regulation of Cell CycleRegulation of Cell Cycle G0
Checkpoints Apoptosis
– Damage Prevention– Developmental
Oncogenes– Mitosis accelerators
Tumor Suppressor Genes– Mitosis brakes
GG00 – Exit From the Cell Cycle – Exit From the Cell Cycle temporary (wbc’s) or permanent (nerve) Cancer cells do not ever enter G0
Checkpoints in the Cell CycleCheckpoints in the Cell Cycle
GG11, SS, and MM occur when cyclinscyclins (proteins) bind & activate kinaseskinases.
Kinases phosphorylate compounds necessary for division.
kinases blocked if damage detected @ GG11, SS, or MM checkpoints.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellCycle.html
p53p53
ATMATM
MADMAD
DNA Damage DetectionDNA Damage Detection GG11
– p53p53, a tumor suppressor, checks for damage before DNA replication
– If damage cannot be repaired, p53 sends cell to to die so it cannot lead to cancer
– P53 mutations implicated in > ½ of all human cancers SS
– ATMATM detects DNA damage, helps p53 send irreparably damaged cells to death, & maintains telomere length
MM– MADMAD stops mitosis if problems w/ microtubles in spindle
fiber formation
APOPTOSISAPOPTOSIS
Programmed Cell Death
DefinitionDefinition Mechanism of normal, controlled death
by:– DNA fragmentation– Cytoplasm shrinkage– Membrane blebbing
Cellular “suicide” No spillage or damage to nearby cells No inflammatory responsehttp://www.sgul.ac.uk/depts/immunology/~dash/apoptosis/apoptosisvideo.html
Is All Cell Death Equal?Is All Cell Death Equal?
Necrosis– Messy cell death usually due to injury– Cellular “homicide”– Cell contents come spilling out leading to an
inflammatory response. • Swelling• Redness• Fever
Why Suicide?Why Suicide?
Development– Mouse paws (and human hands) use cell
death to form digits.
Death As A Necessity For LifeDeath As A Necessity For Life
Immune system cells• Virally infected cells• Immune cells that don’t recognize “self”• Removal of cytotoxic T cells after infection is
conquered
DNA damaged cells• Sent to their death by p53 to prevent tumors
Disorders InvolvedDisorders Involved
Neurological disorders such as Huntington’s, Parkinson’s and Alzheimer’s diseases
• Too much apoptosis
Cancer• Not enough apoptosis
Cell Division Cell Death
Genes in CancerGenes in Cancer OncogenesOncogenes
– Genes known to speed up mitosis– Mitosis accelerators when ON
(phosphorylation)– Cancer results if ON when should be OFF
Tumor Suppressor GenesTumor Suppressor Genes– Mitosis brakes– Tumors result if OFF when should be ON
Can a Cell Divide Forever?Can a Cell Divide Forever?
Normal CellsNormal Cells – NONO– TelomeresTelomeres, buffer zones @ tips of each
chromosome, get shorter w/ each division– Cells die when telomeres gone
• EX: Aging effects are due to dead cells that can no longer be replaced
Can a Cell Divide Forever?Can a Cell Divide Forever? Cancer CellsCancer Cells – YESYES
– Telomerase is ON• Enzyme repairs telomeres after each division
Embryonic Stem CellsEmbryonic Stem Cells – YESYES– Fountain of Youth lies in harnessing anti-
aging powers of telomerase w/o risk of cancer
NO EASY TASKNO EASY TASK
www.hybridmedicalanimation.com http://www.ellisonfoundation.org/images/pfbs/p018_telomeres.jpg
The Cell CycleThe Cell Cycle
http://bhs.smuhsd.org/bhsnew/academicprog/science/vaughn/Student%20Projects/Paul%20&%20Marcus/Cell_Replication.html