the cell cycle
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The Cell CyclePART 2
Honors Genetics
Ms. Gaynor
The Cell Cycle
The mitotic phase alternates The mitotic phase alternates with interphase in the cell cyclewith interphase in the cell cycle InterphaseInterphasemitosismitosisinterphaseinterphasemitosismitosis
Phases of the Cell Cycle
The cell cycle consists ofThe mitotic (M) phaseInterphase (90% of the cell’s
life) INTERPHASEINTERPHASE
GG11
SS(DNA synthesis)(DNA synthesis)
G2Cytoki
nesis
Cytoki
nesis
Mito
sis
Mito
sis
MITOTIC
MITOTIC(M) PHASE
(M) PHASE
Figure 12.5
Interphase can be Interphase can be divided into divided into subphases subphases
GG11 phase (GAP 1 phase) phase (GAP 1 phase) cell grows in sizecell grows in sizevaries most in length from cell to cellvaries most in length from cell to cell
S phase (synthesis phase)S phase (synthesis phase)DNA is copied (DNA replication)DNA is copied (DNA replication)
Single Single Double Double Other organelles are copied Other organelles are copied
(ex: centrosomes in animal cells) (ex: centrosomes in animal cells) GG22 phase (GAP 2 phase) phase (GAP 2 phase)
More growth and preparation (make proteins) for mitosisMore growth and preparation (make proteins) for mitosishttp://www.cellsalive.com/cell_cycle.htmhttp://www.cellsalive.com/cell_cycle.htm
Another G Another G phase of phase of
InterphaseInterphase Called G0 phase called
the resting phase The cell exits the
“cycle” and (usually) does NOT reproduce again
Ex: muscle cells, nerve cells, red blood cells
InterInterphasephase““InterIntermission” or mission” or
““InInbetween” between”
not part of mitosisIncludes stages G1, S, and
G2 of the cell cycleDNA is in chromatin formNucleus & nucleolus presentLongest phase of cell cycle
The Mitotic (M) phaseThe Mitotic (M) phase
Is made up of 2 partsIs made up of 2 parts
1. Mitosis1. Mitosis division of division of the nucleus the nucleus (called (called Karyokinesis) Karyokinesis)
2. Cytokinesis 2. Cytokinesis division of the cytoplasmdivision of the cytoplasm
Mitosis Mitosis Continuous pathway (Early, Mid, &
Late) Consists of 4 phases and cytokinesis
ProphaseMetaphaseAnaphaseTelophase
Cytokinesis
Prophase (X’s)“Pack Together”
Chromatin Chromosomes DNA “packs” together
Mitotic spindle fibers form from centrosomes Centrioles are in centromsomes in animals
appear as asters asters in in aanimalsnimals Microtubule Organizing Centers (MTOC’s) (in
plants) Centrosomes & Spindle fibers move towards
“poles” Late:Late: Nucleus and nucleolus disappear kinetochore fiberskinetochore fibers attach to each kinetochore attach to each kinetochore
onon each each chromosome they begin to migrate toward the cell center
G2 OF INTERPHASE PROPHASE PROMETAPHASECentrosomes(with centriole pairs)
Chromatin(duplicated)
Early mitoticspindle
Aster
CentromereFragmentsof nuclearenvelope
Kinetochore
Nucleolus Nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Kinetochore microtubule Figure 12.6
Nonkinetochoremicrotubules
Mitotic Spindle Fibers Two types of spindle fibers
1.1. Kinetochore fibersKinetochore fibers2.2. Polar fibersPolar fibers
Metaphase (X’s)“Meet in the Middle”
Chromosomes line up in the middle of cell Called equatorial or metaphase
plate Kinetochore spinder fibers pull and tug
chromosomes to line up
Anaphase (V’s)“Adios and Away”
SISTER CHROMATIDS separate and begin moving to opposite ends (poles) of the cell
Polar fibers lengthen and elongate the cell
Late anaphase each pole contains a complete set of single chromosomes
NOTE: This is the only time there is DOUBLE the amount of DNA in ONE cell
In anaphase, sister chromatids separateAnd move along the kinetochore
microtubules toward opposite ends of the cell1
Spindlepole
Kinetochore
Figure 12.8
Centrosome at one spindle pole
Daughter chromosomes
METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS
Spindle
Metaphaseplate
Nucleolusforming
Cleavagefurrow
Nuclear envelopeforming
Figure 12.6
Telophase (V’s)“Two New Cells”
The spindle fibers dissappear
Two daughter nuclei and nucleoli begin to form at the two poles
Nuclear envelopes reforms from the fragments of the parent cell’s nuclear envelope and other portions of the endomembrane system
Chromosomes chromatin
Cytokinesis“Division of the Cytoplasm”
Occurs in Occurs in Late telophaseLate telophase In animal cellsIn animal cells
a a cleavage furrowcleavage furrow forms, which forms, which pinches the cell in two.pinches the cell in two.
In plant cellsIn plant cells vesicles from the Golgi apparatus vesicles from the Golgi apparatus
produce a produce a cell platecell plate at the middle of at the middle of the cellthe cell
At the end of cytokinesis, there are two At the end of cytokinesis, there are two distinct distinct IDENTICALIDENTICAL daughter cells. daughter cells.
Cytokinesis: A Closer Look
In animal cellsCytokinesis occurs by
a process known as cleavagecleavage, forming a cleavage furrow
Cleavage furrow
Contractile ring of microfilaments
Daughter cells
100 µm
(a) Cleavage of an animal cell (SEM)Figure 12.9 A
In plant cells, during cytokinesisIn plant cells, during cytokinesisA cell plate formsA cell plate forms
Daughter cells
1 µmVesiclesforming cell plate
Wall of patent cell Cell plate New cell wall
(b) Cell plate formation in a plant cell (SEM)Figure 12.9 B
G2 OF INTERPHASE PROPHASE PROMETAPHASE
Centrosomes(with centriole pairs)
Chromatin(duplicated)
Early mitoticspindle
Aster
CentromereFragmentsof nuclearenvelope
Kinetochore
Nucleolus Nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Kinetochore microtubule Figure 12.6
Nonkinetochoremicrotubules
Centrosome at one spindle pole
Daughter chromosomes
METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS
Spindle
Metaphaseplate
Nucleolusforming
Cleavagefurrow
Nuclear envelopeforming
Figure 12.6
Mitosis in a plant cell
1 Prophase. The chromatinis condensing. The nucleolus is beginning to disappear.Although not yet visible in the micrograph, the mitotic spindle is staring to from.
Prometaphase.We now see discretechromosomes; each consists of two identical sister chromatids. Laterin prometaphase, the nuclear envelop will fragment.
Metaphase. The spindle is complete,and the chromosomes,attached to microtubulesat their kinetochores, are all at the metaphase plate.
Anaphase. Thechromatids of each chromosome have separated, and the daughter chromosomesare moving to the ends of cell as their kinetochoremicrotubles shorten.
Telophase. Daughternuclei are forming. Meanwhile, cytokinesishas started: The cellplate, which will divided the cytoplasm in two, is growing toward the perimeter of the parent cell.
2 3 4 5
NucleusNucleolus
ChromosomeChromatinecondensing
Figure 12.10
Cell Cycle and Mitosis Animations
http://www.ucopenaccess.org/courses/APBiologyI/course%20files/multimedia/lesson17/lessonp.html
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120073/bio14.swf::Mitosis%20and%20Cytokinesis
http://www.sumanasinc.com/webcontent/animations/content/mitosis.html
http://www.johnkyrk.com/mitosis.html
Remember…“IPMATc”
I peed on the mat, see.Let’s do the Mitosis Hand
Cheer!
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