MITOSIS
Phase in which cell doubles in
size and DNA content
Interphase
Phases of Interphase
G1
S
G2
Quiescent phase no more
synthesis occurs
G0
G1
S
G2
-period
period of after mitosis
-RNA
RNA and Protein synthesis
-Cyclin
Cyclin D & E bind to Cyclin
Dependent Kinase (CDK) to
initiate progression to S
- DNA replication
- Protein synthesis
- Chromosomal duplication
- Centromere duplication
- Cyclin A binds to CDK to enter
G2
-2-4 hours
-Centrioles grow
-Energy
Energy for mitosis stored
-RNA
RNA and Proteins for mitosis
synthesized
-Tubulin
Tubulin for spindle apparatus
synthesized
-Cyclin
Cyclin B initiates entry to M
phase
Mitosis
Prophase
Centrosome
-2
2 identical daughter cells
-Prophase
-Prometaphase
-Metaphase
-Anaphase
-Telophase
-nuclear
nuclear envelope and nucleolus
begin to disappear
-chromosomes
omes condense
-2
2 sister chromatids attached at
centromere
-Centrioles
Centrioles migrate to opposite
poles giving rise to astral rays
and spindle fibers
-DNA
DNA = 4n (doubled)
-centrioles
tubulin rings in a cloud
-α-tubulin
-Microtubule
Microtubule Organizing Center
(MTOC)
Chromosome
-2
2 parallel sister chromatids
attached at centromere
-Kinetochores
Kinetochores form at
centromeres, MTOC
Prometaphase
-nuclear
nuclear envelope disappears
-kinetochore
kinetochore microtubules form
-polar
polar microtubles (spindle mt not
attached to kinetochore)
Metaphase
-chromosomes
chromosomes align at equatorial
plate of mitotic spindle and attach
to spindle mt at kinetochore
-4n DNA
Anaphase
-chromatids separate at
centromere cohesion degrades,
spindle elongates
-4n DNA
-Contractile ring of actin
microfilaments forms around cell
Anaphase A
-kinetochores shorten, pulling
daughters to poles
-(-) end directed motor protein at
kinetochore
Anaphase B
-overlapping polar mt slide
against each other pushing on
opposite pole and pulling towards
its own pole
-(-) end directed motor proteins at
astral mt. binding to cell cortex
-(+) end directed motor proteins
at midbody of overlapping polar
mt.
Telophase
Microtubules
-each daughter reaches a pole
cytokinesis◊-mt in the
overlapping polar midbridge mt
depolymerize
-nuclear envelope reforms
-nucleoli reappear
-cell returns to interphase
appearance
-2n DNA
-Mitotic spindle
-Polar: go toward the equatorial
plane
-Astral: go towards one end of
pm
-Kinetochore: from the
centromere
-Grow towards (+) end
-No spindle no cell division, so
cancer drug target
-Taxol: stabilizes mt. so no
division
-Anti-MT: Colchichine;
Vinblastine; Nocodazole
-contactile ring during cytokinesis
-bipolar myosin II filaments slide
actin against itself
Actin
Intermediate Filaments
-breakdown of and reassembly of
nuclear envelope
-phophorylation of lamins triggers
disassembly of nuclear lamina
-P added around prophase, and
removed after prophase
Fate of Organelles in Mitosis
-ER, Golgi vesiculate when
nuclear envelope breaks down,
reform in telophase
-Mitochondira, peroxisomes and
lysosomes remain unchanged
MEIOSIS
Meiosis 1
homologous chromosomes are separated
into two daughter cells ; follows stages
similar to Mitosis.
Prophase 1
Chromosomes form and each
chromosome pairs with its homologous
chromosome; called a tetrad (four
chromatids) In a tetrad, homologous
chromosomes can exchange portions of
their chromatids; called crossing over.
Metaphase 1
Tetrads line up in the middle, equatorial
plane,of the cell
Anaphase 1
Homologous chromosomes separate and
move away from each other to opposite
poles of the cell. Each is genetically
different from the original cell due to
crossing over.
Telophase & Cytokinesis 1
nuclear envelope forms ; cytokinesis
occurs resulting in two daughter cells.
Daughter cells are NOT identical due to
crossing over in prophase 1
Meiosis 2
sister "recombinant" chrimatids are
seperated into four gamete cells; follows
stages similar to mitosis.
Prophase 2
chromosomes form; nuclear envelope
disappears
metaphase 2
chromosomes line up in the middle of the
cell at the equatorial plate.
Anaphase 2
Sister chromatids separate and move
away from each other to opposite poles of
the cell
Telophase & Cytokinesis 2
nuclear envelope forms; Cytokinesis
occurs resulting in four genetically
different gametes