Cells divide through the process of mitosis in order to repair and replace old or damaged cells, to grow, and to develop multicellular organisms. Mitosis consists of prophase, metaphase, anaphase and telophase where the genetic material and cytoplasm are divided to form two identical daughter cells. The cell cycle, which is the life of a cell, includes interphase where the cell grows and duplicates its DNA in preparation for division, and M-phase where mitosis and cytokinesis occur. The cell cycle is tightly regulated by internal factors such as cyclins and cyclin-dependent kinases and external growth factors to ensure cells only divide when necessary.

1. MitosisWhy do cells need to divide?

3. Recap…Cell theory…Cells are the basic structural unit of lifeCells are the functional units of lifeCells come from pre-existing cells

4. OverviewWhy do cells need to divide?Repair, growth, developmentTypes of reproductionSexualGenetically different2 parentsTakes time to develop, better chance of survival asexualGenetically identicalOne parentMany offspring very quickly

5. DNABlueprint of life, nucleic acidChromatinGranular genetic material, spread out in nucleus of non-dividing cellsChromosomesCondensed genetic material, in dividing cellsSister chromatidsIdentical copies of Chromosomes joined by a centromere (“centro-” middle)

8. Humans46 chromosomes 46 sister chromatidsOne from your mom, one from your dad

9. Cell Cycle: Life of a Cell

10. Cell CycleInterphase90 % of cell’s life, non dividingG1 phaseGrows, makes organellesS phaseDNA Synthesis…DNA replicatesG2 phaseCell prepares to divide, makes sure it has all important organelles for divisionM phaseWhen the cytoplasm and nucleus of the cell divides

11. Cell CycleThere are check points in G1, S, and G2Make sure cell is ready to move onto the next phase (has all necessary organelles, copied DNA, etc.)Once the cell has past the G1 checkpoint, it will complete the cell cycleSome cells stay in the G1 phase all their life (muscle cell, brain cells)

12. Regulators of Cell CycleCyclinsProtein that regulates the timing of the cell cycle in eukaryotic cellsLevels of cyclins rise and fall throughout the cell cycleCyclin-dependent Kinases (cdks)Enzymes that are activated when they bind with cyclin and they make the cell cycle continue

14. RegulatorsInternalFactors within the cell that control cell cycleCyclin and CDKsAllow cell cycle to proceed only when certain processes have occurredReplication of chromosomesChromosome Attachment to spindle before anaphase ExternalFactors Outside the cellGrowth factorsmolecules that bind to cell surface that signal cell to divideSimilar cells have molecules that have opposite effect so that when it becomes to crowded, cells stop dividing

19. M-phaseConsists of mitosis and cytokinesisMitosisProcess by which the nucleus of a cell dividesOne parent cell makes two identical daughter cellsThis is how organisms repair tissue and grow and developCytokinesis-division of the cytoplasm

20. Depending on cell type…Mitosis can take a few minutes or a few daysMuscle cells (non-dividing)Nerve cells (non-dividing)Skin cells (divide all the time)Digestive Tract cells (divide all the time)

21. Life Span of Some Human Cells

22. Easy way to remember M-PhasePMAT Pilates Make Annie TonedPractice Makes Athletes TrainProphaseMetaphaseAnaphaseTelophase

23. Prophase50-60% of timeChromosomes become visibleCentrioles develop in cytoplasm near nuclear envelopeCentrioles separate and migrate to opposite ends of nuc. Env.CentrosomeRegion where Centrioles are foundOrganize the “spindle”Fan like microtubule structure that helps separate chromosomesPlants do NOT have Centrioles

26. End of prophaseChromosomes coil together tightlyNucleolus disappearsNuclear envelope breaks down

27. MetaphaseFew minutesChromosomes line up in middle (M in metaphase MIDDLE)Microtubules connect centromere of each chromosome to the 2 poles of spindle

31. AnaphaseCentromeres joining sister chromatids separate and become individual chromosomesThey are dragged by fibers to opposite polesEnds when chromosomes stop moving

35. TelophaseOpposite of prophaseCondensed chromosomes disperse into tangle of materialNuclear envelope reformsSpindle breaks apartNucleolus becomes visibleAt the end 2 identical nuclei in one cell

39. CytokinesisHappens at the same time as TelophaseDivision of cytoplasmAnimal CellsCell membrane drawn inward until it pinches off and forms 2 id daughter cellsPlant CellsCell plate forms between nucleiCell Plate develops into separate membrane Cell wall appears

45. Regulators of Cell CycleCyclinsProtein that regulates the timing of the cell cycle in eukaryotic cellsLevels of cyclins rise and fall throughout the cell cycleCyclin-dependent Kinases (cdks)Enzymes that are activated when they bind with cyclin and they make the cell cycle continue

46. RegulatorsInternalFactors within the cell that control cell cycleCyclin and CDKsAllow cell cycle to proceed only when certain processes have occurredReplication of chromosomesChromosome Attachment to spindle before anaphase ExternalFactors Outside the cellGrowth factorsmolecules that bind to cell surface that signal cell to divideSimilar cells have molecules that have opposite effect so that when it becomes to crowded, cells stop dividing