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!