mitosis “nuclear division” - ms. brammer's webpageshaunab.info/ap biology/unit...
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AP Biology
Mitosis “Nuclear division”: § Dividing cell’s DNA between
2 daughter nucleiu “dance of the chromosomes”
§ 4 phasesu prophaseu metaphaseu anaphaseu telophase
AP Biology
Prophase: § Chromatin condenses
u visible chromosomes§ chromatids
§ Centrioles move to opposite poles of cell u animal cell
§ Protein fibers cross cell to form mitotic spindleu microtubules
§ actin, myosin u coordinates movement of chromosomes
§ Nucleolus disappears
green = key features
AP Biology
Transition to Metaphase: § Prometaphase§ Nuclear membrane breaks down
u spindle fibers attach to centromeres§ creating kinetochores
u microtubules attach at kinetochores § connect centromeres to centrioles
u chromosomes begin moving
green = key features
AP Biology
Metaphase: § Chromosomes align along
middle of cellu metaphase plate
§ meta = middle u spindle fibers coordinate movementu helps to ensure chromosomes
separate properly§ so each new nucleus receives only
1 copy of each chromosome
green = key features
AP Biology
AP Biology
Anaphase: § Sister chromatids separate at
kinetochores u move to opposite polesu pulled at centromeresu pulled by motor proteins
“walking” along microtubules§ actin, myosin§ increased production of
ATP by mitochondria§ Poles move farther apart
u polar microtubules lengthen
green = key features
AP Biology
Separation of chromatids:§ In anaphase, proteins holding together sister
chromatids are inactivatedu separate to become individual chromosomes
2 chromosomes1 chromosome2 chromatids single-stranded
double-stranded
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§ Pac-man mechanism: Kinetochores use motor proteins that “walk” chromosome along attached microtubuleu microtubule shortens by
dismantling at kinetochore (chromosome) end
Chromosome movement:2 mechanisms -
§ Reel-in mechanism: microtubules “reel in” to centrioles like a line on a fishing rod
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Telophase:§ Chromosomes arrive at
opposite polesu daughter nuclei formu nucleoli formu chromosomes disperse
§ no longer visible under light microscope
§ Spindle fibers disperse§ Cytokinesis begins
u cell division
green = key features
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Cytokinesis:§ Animals
u constriction belt of actinmicrofilaments around equator of cell§ cleavage furrow forms§ splits cell in two§ like tightening a draw
string
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Cytokinesis in Animals:
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Mitosis in whitefish blastula:
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Mitosis in animal cells:
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Cytokinesis in Plants:§ Plants
u cell plate forms§ vesicles line up at equator
w derived from Golgi§ vesicles fuse to form 2 cell
membranesu new cell wall laid down
between membranes§ new cell wall fuses with
existing cell wall
AP Biology
Cytokinesis in plant cell:
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Mitosis in plant cell:
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onion root tip
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Origin of replication
chromosome:double-stranded DNA replication
of DNA
elongation of cell
cell pinches in two
ring of proteins
Evolution of mitosis:
§ Mitosis in eukaryotes likely evolved from binary fission in bacteriau single circular
chromosomeu no membrane-bound
organelles
AP Biology
§ A possible progression of mechanisms intermediate between binary fission & mitosis seen in modern organisms
protistsdinoflagellates
protistsdiatoms
eukaryotesyeast
eukaryotesanimals
prokaryotes(bacteria)Evolution of mitosis:
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Dinoflagellates: § algae
u “red tide”u bioluminescence
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Diatoms: § microscopic algae
u marineu freshwater
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Control of Cell Cycle:
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Kinetochore: § Each chromatid
has own kinetochore proteinsu microtubules
attach to kinetochore proteins
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nucleosomeDNAhistone
DNA double helixchromosome
rosettes ofchromatin loops
scaffoldprotein
chromatin loop
30 nm
Chromosome structure:
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G2
S G1
Mmetaphase
prophaseanaphase
telophase
interphase (G1, S, G2 phases)mitosis (M)cytokinesis (C)
C
§ Phases of a dividing cell’s life u interphase
§ cell grows§ replicates chromosomes§ produces new organelles, enzymes, membranes…§ G1, S, G2
u mitotic phase§ cell separates & divides chromosomes
w mitosis§ cell divides cytoplasm & organelles
w cytokinesis
Cell Division cycle:
AP Biology
How did you get from there
to here?
1 cell to 100 trillion cells!
And now look at you…
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