How Cells Divide Chapter 10. Bacterial Cell Division Binary Fission FtsZ protein.
Cellular Division. 2 Binary Fission DNA replicated Membrane added.
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Transcript of Cellular Division. 2 Binary Fission DNA replicated Membrane added.
Cellular DivisionCellular Division
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Binary FissionBinary Fission
DNA replicated
Membrane added
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Cell DivisionCell Division
Functions in Reproduction, Growth, and RepairFunctions in Reproduction, Growth, and Repair• Unicellular OrganismsUnicellular Organisms
• Reproduction of Entire OrganismsReproduction of Entire Organisms• Multicellular OrganismsMulticellular Organisms
• Growth and Development from the Fertilized EggGrowth and Development from the Fertilized Egg• Replacement of Damaged or Dead CellsReplacement of Damaged or Dead Cells
• Distributes Identical Sets of ChromosomesDistributes Identical Sets of Chromosomes• Precisely Replicates its DNAPrecisely Replicates its DNA• Results in 2 Daughter CellsResults in 2 Daughter Cells
4Binary Fission in Bacterium:Binary Fission in Bacterium:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis
Division planeDivision plane
Cell wallCell wall
CytoplasmCytoplasm
NuclearNuclearmaterialmaterial
5Binary Fission in Paramecium:Binary Fission in Paramecium:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis
New individualsNew individuals
6Budding Yeast:Budding Yeast:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis
Nucleus divides by Nucleus divides by mitosis.mitosis.
Bud forms on cell.Bud forms on cell.Nucleus moves into Nucleus moves into
bud.bud.Bud separates.Bud separates.
7Budding Hydra:Budding Hydra:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis
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Mitotic Mitotic
cell cell divisiondivision
Mitotic Mitotic cell cell division & division &
differ-differ-entiationentiation
Growth and Development:Growth and Development:Functions of MitosisFunctions of Mitosis
TissuesTissues
OrgansOrgansFertilized eggFertilized egg(zygote)(zygote) Multicell stageMulticell stage
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telophase
metaphase
anaphase
cell
divi
sion
GG00: nondividing: nondividing
interphaseinterphase
The EukaryoticThe EukaryoticCell CycleCell Cycle
S: Synthesis S: Synthesis of DNA; of DNA; chromosomes chromosomes duplicatedduplicated
GG11: Growth: Growth
GG22: Growth: Growth
prophase
cytokinesis
Mito
sis
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The Cell CycleThe Cell Cycle
Alternates between mitotic (M) phase and Alternates between mitotic (M) phase and interphase in eukaryotes.interphase in eukaryotes.
InterphaseInterphase– ~90% of cycle~90% of cycle– chromosome replicationchromosome replication– cell growth and metabolismcell growth and metabolism– three periodsthree periods
1.1. G1 phase – first growth phaseG1 phase – first growth phase2.2. S phase – synthesis of duplicated DNAS phase – synthesis of duplicated DNA3.3. G2 phase – second growth phaseG2 phase – second growth phase
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Interphase : The chromosomes (blue) are in the thin, extended state and appear as a mass in the center of the cell. The microtubules (red) extend outward from the nucleus to all parts of the cell.
Interphase (nondividing)Interphase (nondividing)
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Interphase : The chromosomes (blue) are in the thin, extended state and appear as a mass in the center of the cell. The microtubules (red) extend outward from the nucleus to all parts of the cell.
Late prophase: Chromosomes have condensed and attached to microtubules. Microtubules have reorganized to form the spindle. Chromatid develops a kinetechore.
Phases of Mitosis (nuclear division): Phases of Mitosis (nuclear division): ProphaseProphase
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11 single-stranded chromosomesingle-stranded chromosome22 double helixdouble helix
uncondenseduncondensed
DNA replicationDNA replication
11 double-stranded chromosomedouble-stranded chromosome22 double helicesdouble helices
still uncondensedstill uncondensed
Chromosome Chromosome condensationcondensation
11 double-stranded chromosomedouble-stranded chromosome22 double helicesdouble helices
now condensednow condensed
centromere centromere aachromatidchromatid
cellcell basebasepairspairs
closer lookstill closer lookeven closer look
Chromosome CondensationChromosome Condensation
14HumanHumanChromosomes during MitosisChromosomes during Mitosis
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Human Karyotype, MaleHuman Karyotype, Male
These are These are chromosomes from chromosomes from mitosismitosis
Stained to show Stained to show regionsregions
Numbered by lengthNumbered by lengthOccur in pairsOccur in pairs
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Interphase : The chromosomes (blue) are in the thin, extended state and appear as a mass in the center of the cell. The microtubules (red) extend outward from the nucleus to all parts of the cell.
Metaphase: The chromosomes have moved along the spindle microtubules to the equator of the cell. Centromeres align on the equator. Entire structure of microtubules is called the spindle.
Late prophase: Chromosomes have condensed and attached to microtubules. Microtubules have reorganized to form the spindle. Chromatid develops a kinetechore.
Phases of Mitosis (nuclear division):Phases of Mitosis (nuclear division):MetaphaseMetaphase
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Separation of Sister ChromatidsSeparation of Sister Chromatids
In metaphase, sister chromatids In metaphase, sister chromatids are held together at centromereare held together at centromere
At end of metaphase, centromere At end of metaphase, centromere releases sister chromatidsreleases sister chromatids
In anaphase, they move to opposite In anaphase, they move to opposite polespoles
In metaphase, sister chromatids In metaphase, sister chromatids are held together at centromereare held together at centromere
At end of metaphase, centromere At end of metaphase, centromere releases sister chromatidsreleases sister chromatids
In anaphase, they move to opposite In anaphase, they move to opposite polespoles
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Anaphase: Sister chromatids have separated into separate chromosomes. Kineteochore microtubules shorten at kinetochore. Poles move farther apart.
Telophase: Nonkinetochore microtubules elongate cell. The chromosomes have gathered into two clusters, one at the site of each future nucleus.
Next interphase: Chromosomes are relaxing again into their extended state. Spindle fibers are disappearing, and the microtubules of the 2 daughter cells rearrange into the interphase pattern.
Phases of Mitosis:Phases of Mitosis:Anaphase & TelophaseAnaphase & Telophase
19Mitosis:Mitosis:Prophase - MetaphaseProphase - Metaphase
Kinetochores align at cell’s
equator
Nucleolus disappears;
Nuclear envelope breaks down
Microtubules attach to
kinetochores
Chromosomes condense and
shorten
Centrioles begin to move apart;Spindle forms
Duplicated chromosomes
remain elongated
Centrioles have also been duplicated
LateLateInterphaseInterphase
EarlyEarlyProphaseProphase
LateLateProphaseProphase MetaphaseMetaphase
20MitosisMitosisAnaphase - CytokinesisAnaphase - Cytokinesis
Free spindle fibers push poles apart
Chromatids become
independent chromosomes
One set of chromosomes;
Begin unwinding
Nuclear envelope re-
forms
Cytoplasm divided along
equator
Each daughter gets 1 nucleus &
half of cytoplasm
Spindle disappears; Nucleolus reappears
AnaphaseAnaphase TelophaseTelophase CytokinesisCytokinesisNextNext
InterphaseInterphase
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Cytokinesis of a Ciliated CellCytokinesis of a Ciliated Cell
Cleavage FurrowCleavage Furrow
Daughter CellsDaughter Cells
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Cytokinesis in PlantsCytokinesis in Plants
Vesicles fuse to form cell wall
and membranesComplete
separation of daughter cells
23Mitosis, Meiosis,Mitosis, Meiosis,and the Sexual Cycleand the Sexual Cycle
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Meiosis IMeiosis IHomologous
chromosomes pair and cross over
Homologous chromosomes
exchange DNA & align on equator
Homologous chromosomes move to
opposite poles
Prophase IProphase I Metaphase IMetaphase I Anaphase IAnaphase I Telophase ITelophase I
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Meiosis IIMeiosis II
Prophase IIProphase II Metaphase IIMetaphase II Anaphase IIAnaphase II Telophase IITelophase IIFourFour
HaploidHaploidCellsCells
Similar to MitosisSimilar to Mitosis
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Crossing OverCrossing Over
Homologues Homologues pair uppair up
Protein strands Protein strands zip togetherzip together
Recombination Recombination enzymes snip enzymes snip and rejoin and rejoin DNADNA
Homologs Homologs separate with separate with new gene new gene combinationscombinations
27Meiosis vs. Mitosis:Meiosis vs. Mitosis:Comparison of SpindlesComparison of Spindles
Meiosis: Duplicated chromosomes Meiosis: Duplicated chromosomes with one kinetochore; Paired with one kinetochore; Paired homologues go to opposite poles.homologues go to opposite poles.
Meiosis: Duplicated chromosomes Meiosis: Duplicated chromosomes with one kinetochore; Paired with one kinetochore; Paired homologues go to opposite poles.homologues go to opposite poles.
Mitosis: Duplicated chromosomes Mitosis: Duplicated chromosomes with two kinetochores; Unpaired with two kinetochores; Unpaired homologs split between sister homologs split between sister chromatids, which go to opposite chromatids, which go to opposite poles.poles.
Mitosis: Duplicated chromosomes Mitosis: Duplicated chromosomes with two kinetochores; Unpaired with two kinetochores; Unpaired homologs split between sister homologs split between sister chromatids, which go to opposite chromatids, which go to opposite poles.poles.
28Meiosis vs. Mitosis:Meiosis vs. Mitosis:Comparison of StagesComparison of Stages
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Metaphase Alignment ScenariosMetaphase Alignment Scenarios
The endThe end