3 Where it all began…You started as a cell smaller than a period at the end of a sentence…
4 How did you get from there to here? And now look at you…How did you get from there to here?
5 Getting from there to here… Going from egg to baby….the original fertilized egg has to divide…and divide…
6 Why do cells divide? For reproduction For growth For repair & renewal asexual reproductionone-celled organismsFor growthfrom fertilized egg to multi-celled organismFor repair & renewalreplace cells that die from normal wear & tear or from injuryamoebaUnicellular organismsCell division = reproductionReproduces entire organism& increase populationMulticellular organismsCell division provides for growth & development in a multicellular organism that begins as a fertilized eggAlso use cell division to repair & renew cells that die from normal wear & tear or accidents
7 Making new cells Nucleus Cytoskeleton chromosomes DNA centrioles in animalsmicrotubule spindle fibers
8 What kind of molecules need to pass through? histone proteinchromosomeDNANucleusFunctionprotects DNAStructurenuclear envelopedouble membranemembrane fused in spots to create poresallows large macromolecules to pass throughnuclearporesporenuclear envelopenucleolusWhat kind of molecules need to pass through?
14 Getting the right stuff What is passed on to daughter cells?exact copy of genetic material = DNAmitosisorganelles, cytoplasm, cell membrane, enzymescytokinesischromosomes (stained orange) in kangaroo rat epithelial cellnotice cytoskeleton fibers
15 Overview of mitosis I.P.M.A.T. interphase prophase (pro-metaphase) cytokinesismetaphaseanaphasetelophase
16 Time to divide & multiply! Interphase90% of cell life cyclecell doing its “everyday job”produce RNA, synthesize proteins/enzymesprepares for duplication if triggeredI’m working here!Time to divide & multiply!
17 Cell cycle Cell has a “life cycle” cell is formed from a mitotic divisioncell grows & maturesto divide againcell grows & matures to never divide againG1, S, G2, Mliver cellsG1G0epithelial cells, blood cells,stem cellsbrain / nerve cellsmuscle cells
18 Interphase Divided into 3 phases: G0 G1 = 1st Gap (Growth) cell doing its “everyday job”cell growsS = DNA Synthesiscopies chromosomesG2 = 2nd Gap (Growth)prepares for divisioncell grows (more)produces organelles, proteins, membranesG0signal to divide
19 Interphase Nucleus well-defined Prepares for mitosis green = key featuresInterphaseNucleus well-definedDNA loosely packed in long chromatin fibersPrepares for mitosisreplicates chromosomeDNA & proteinsproduces proteins & organelles
20 S phase: Copying / Replicating DNA Synthesis phase of Interphasedividing cell replicates DNAmust separate DNA copies correctly to 2 daughter cellshuman cell duplicates ~3 meters DNAeach daughter cell gets complete identical copyerror rate = ~1 per 100 million bases3 billion base pairs in mammalian genome~30 errors per cell cyclemutations (to somatic (body) cells)
21 Organizing DNA DNA is organized in chromosomes ACTGGTCAGGCAATGTCDNAOrganizing DNADNA is organized in chromosomesdouble helix DNA moleculewrapped around histone proteinslike thread on spoolsDNA-protein complex = chromatinorganized into long thin fibercondensed further during mitosishistoneschromatindouble stranded chromosomeduplicated mitotic chromosome
22 Copying DNA & packaging it… After DNA duplication, chromatin condensescoiling & folding to make a smaller packageDNAmitotic chromosomechromatin
24 Mitotic Chromosome Duplicated chromosome 2 sister chromatids narrow at centromerescontain identical copies of original DNAhomologouschromosomeshomologouschromosomesCentromeres are segments of DNA which have long series of tandem repeats = 100,000s of bases long. The sequence of the repeated bases is quite variable. It has proven difficult to sequence.sister chromatidssingle-strandedhomologous = “same information”double-stranded
25 Mitosis Dividing cell’s DNA between 2 daughter nuclei 4 phases “dance of the chromosomes”4 phasesprophasemetaphaseanaphasetelophase
26 Prophase Chromatin condenses visible chromosomes green = key featuresProphaseChromatin condensesvisible chromosomeschromatidsCentrioles move to opposite poles of cellanimal cellProtein fibers cross cell to form mitotic spindlemicrotubulesactin, myosincoordinates movement of chromosomesNucleolus disappearsNuclear membrane breaks down
27 Transition to Metaphase green = key featuresTransition to MetaphasePrometaphasespindle fibers attach to centromerescreating kinetochoresmicrotubules attach at kinetochoresconnect centromeres to centrioleschromosomes begin moving
28 Metaphase Chromosomes align along middle of cell metaphase plate green = key featuresMetaphaseChromosomes align along middle of cellmetaphase platemeta = middlespindle fibers coordinate movementhelps to ensure chromosomes separate properlyso each new nucleus receives only 1 copy of each chromosome
30 Anaphase Sister chromatids separate at kinetochores green = key featuresAnaphaseSister chromatids separate at kinetochoresmove to opposite polespulled at centromerespulled by motor proteins “walking”along microtubulesactin, myosinincreased production of ATP by mitochondriaPoles move farther apartpolar microtubules lengthen
31 Separation of chromatids In anaphase, proteins holding together sister chromatids are inactivatedseparate to become individual chromosomes1 chromosome2 chromatids2 chromosomessingle-strandeddouble-stranded
32 Chromosome movementKinetochores use motor proteins that “walk” chromosome along attached microtubulemicrotubule shortens by dismantling at kinetochore (chromosome) endMicrotubules are NOT reeled in to centrioles like line on a fishing rod.The motor proteins walk along the microtubule like little hanging robots on a clothes line.In dividing animal cells, non-kinetochore microtubules are responsible for elongating the whole cell during anaphase, readying fro cytokinesis
33 Telophase Chromosomes arrive at opposite poles Spindle fibers disperse green = key featuresTelophaseChromosomes arrive at opposite polesdaughter nuclei formnucleoli formchromosomes disperseno longer visible under light microscopeSpindle fibers disperseCytokinesis beginscell division
34 CytokinesisAnimalsconstriction belt of actin microfilaments around equator of cellcleavage furrow formssplits cell in twolike tightening a draw stringDivision of cytoplasm happens quickly.
35 Cytokinesis in Animals (play Cells Alive movies here)(play Thinkwell movies here)
38 Cytokinesis in Plants Plants cell plate forms vesicles line up at equatorderived from Golgivesicles fuse to form 2 cell membranesnew cell wall laid down between membranesnew cell wall fuses with existing cell wall
42 Origin of replicationchromosome:double-stranded DNAreplicationof DNAelongation of cellcell pinches in tworing of proteinsEvolution of mitosisMitosis in eukaryotes likely evolved from binary fission in bacteriasingle circular chromosomeno membrane-bound organelles
43 prokaryotes(bacteria)Evolution of mitosisprotists dinoflagellatesA possible progression of mechanisms intermediate between binary fission & mitosis seen in modern organismsprotists diatomseukaryotesyeastProkaryotes (bacteria)No nucleus; single circular chromosome. After DNA is replicated, it is partitioned in the cell. After cell elongation, FtsZ protein assembles into a ring and facilitates septation and cell division.Protists (dinoflagellates)Nucleus present and nuclear envelope remains intact during cell division. Chromosomes linear. Fibers called microtubules, composed of the protein tubulin, pass through tunnels in the nuclear membrane and set up an axis for separation of replicatedchromosomes, and cell division.Protists (diatoms)A spindle of microtubules forms between two pairs of centrioles atopposite ends of the cell. The spindle passes through one tunnel in the intact nuclear envelope. Kinetochore microtubules form between kinetochores on the chromosomes and the spindlepoles and pull the chromosomes to each pole.Eukaryotes (yeast)Nuclear envelope remains intact; spindle microtubules form inside the nucleus between spindle pole bodies. A single kinetochore microtubule attaches to each chromosome and pulls each to a pole.Eukaryotes (animals)Spindle microtubules begin to form between centrioles outside of nucleus. As these centrioles move to the poles, the nuclear envelope breaks down, and kinetochore microtubules attach kinetochores of chromosomes to spindle poles. Polar microtubules extend toward the center of the cell and overlap.eukaryotesanimals
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