Cell Cycle

Just what does a cell do with all its time?

Honors Biology Chapter 8

Cell Division

• Cell undergoes reproduction• Makes “daughter cells”• Has to first duplicate its chromosomes• WHY?• To keep the same number of

chromosomes after division

gbAsexual ReproductionTypes of Asexual Reproduction

• One parent• 2 offspring• Offspring identical to

parents (if no mutations)• Mitosis (eukaryotes)• Binary fission

(prokaryotes + unicellular organisms)

• Makes somatic cells (non sex cells)

Sexual Reproduction

• 2 parents• 4 offspring• Offspring most likely

different from parents• Meiosis (multicellular

eukaryotes)• Makes sex cells

Types of Asexual ReproductionBudding

• an offspring grows out of the body of the parent.

• Hydra• budding hydra (10 secs)• Budding in Hydra (1:27)• Spongebob

Regeneration

Starfish regeneration

Regrowth of a limb or organ after damage (not a form of reproduction of whole organism)

Asexual ReproductionParthenogenesis• growth and development

of embryos occur without fertilization.

• Aphid Parthenogenesis (Gotta see this one!!!!!!!)

• Eviction of Drone Bees (5:13)• Komodo Dragon Parthenogen

esis Reproduction

Asexual ReproductionFragmentation

Planaria Regeneration

Body of parent breaks into distinct pieces, each of which can produce an offspring (is a form of reproduction)

Asexual ReproductionGemmules (internal buds)

• internally-produced, asexual bud (new sponge – even if adult does not survive)- usually under stress

-Sexual reproduction of the sponge

-Sponges: Facts

• Internal budding of coral (mushroom coral 55 secs.)

Asexual Reproduction: Vegetative (no seeds or spores)

In Plants• Rhizomes• Tubers• Bulb• Corm

TUBERS

Asexual Vegetative Propagation

Asexual Reproduction

Paramecium (a protist)• Paramecium Binary fissio

n

Amoeba (a protist)• Binary Fission in amoeba• Amoeba division (1:55)

Asexual ReproductionSpores in Plants and Fungi• Little black dots of bread

mold are spores (becomes an organism)

Mold spore dispersal

Mold spore dispersal youtube• Powder inside a puffball

is actually the spores

Yeast buddingSmall growth becomes full yeast cell

yeast budding time lapse

Cell enlarges and splits in half

binary fission of bacteria

Bacteria Binary Fission

Recap: Asexual ReproductionBinary Fission

• Division of a cell (prokaryotes and unicellular organisms) into two identical cells

Mitosis

• a eukaryotic cell separates the chromosomes in its nucleus into two identical nuclei.

•

BINARY FISSION

• 1-Chromosome

duplicates• 2-cell elongates

as chromosomes

move to poles• 3-plasma membrane

moves inward and cell wall is madeYou Tube Binary Fission

For prokaryotes and unicellular protists

Mitosis: How eukaryotes divide

Must divide the genetic material

ALL DNA + ProteinCHROMATINLooseDuring non-division

Not visible with light microscope

CHROMOSOMESingle strandedSomewhat coiledVisible with microscope

• CHROMATID• Paired homologous

chromosomes during cell division

• Densely coiled• Visible with microscope

Chromosomes and centromeres

• Each chromosome strand has its own centromere

Centromere: constricted area of two sister chromatids

Sister Chromatids:Identical copies of Genetic Material

Happens during S phase

• During cell division, the DNA replicates. The replicating DNA molecules attach to the plasma membrane. As the cell elongates, the chromosomes are pulled apart.

• Prokaryotes• No membrane around

nucleus• Simpler• Smaller• Single chromosome• Divide by binary

fission

• Eukaryotes• Membrane around

nucleus• More complex• Larger• Many chromosomes• Divide by mitosis or

meiosis

How many genes?Genes: working subunits of DNA.

• In a human cell• ~21,000

• In a bacterial cell• ~3,000

Sexual Reproduction

-Used to make egg and sperm (that will join later)

-Increases

diversity

Asexual Reproduction

• Used to replace dead cells

• Growth of new parts (size)

• New organism identical to parent

Cell Cycle Game• Enter the Cell Cy

cle Game• Nobelprize.org• (use Firefox )• “Educational

Games”• Scroll down to • Cell cycle game• FUN!!!!!!!!!!!!!!!!!

Top 10 most visited educational games

1. The Blood Typing Game2. The Laser Challenge Game3. The DNA - the Double Helix Game4. The Pavlov's Dog Game5. The Diabetic Dog Game6. The Lord of the Flies Game7. The Electrocardiogram Game8. The Immune System Game9. The Control of the Cell Cycle Game10. The Split Brain Experiments Game

Cell Cycle• = Time from when a cell is first formed

from its dividing parent cell to its own division into daughter cells.

• Cell Division and Cell Cycle Sit back and relax and enjoy the big picture of cell division (5.5 mins)

Cell Cycle• Time from first formed from a dividing

parent to until its own cell division• mcgraw-hill cell cycle

Get out your worksheet to fill out what happens in each phase (back of Nobelprize.org “cell cycle game”

• Eukaryotic Cell Cycle You Tube (4:20)• Interphase = G1, S, G2 = 90% of time

• Mitosis= cell divides = 10% of time

What phases make up interphase? (G1, S, G2)

G1

• Growth of the Cell • Makes more organelles

(mitochondria and ribosomes)• Plasma membrane got larger

(needs more lipids, carbos, proteins)

• High energy activity (cell resp.)• FYI Typical cell 8-10 hours

Go

• Resting or Permanently

no division• Maximum Surface area/volume

EXAMPLES: Nerve (brain) cells• Muscle• OR * Liver (will exit Go if damaged)Go

S Phase

• DNA synthesis

(replicates, makes a copy)• At the end the chromosomes

consist of sister chromatids• FYI Typical cell 6-8 hours

G2

• Growth for mitosis• Check for DNA accuracy• Final prep before mitosis• Centrosome Doubles

(MTOC)• FYI Typical cell 4-6hours

• McGraw-Hill: How the cell cycle works

• Which of the following represents the correct order of the phases of the cell cycle?

• A) G1 -> G2 -> S -> M

• B) G1 -> G2 -> M -> S

• C) G1 -> S -> G2 -> M

• D) G1 -> S -> M -> G2

• E) G1 -> M -> G2 -> S

Can you tell what goes on in each?

• Cell Cycle Movie

• Try this one…"The Cell Cycle" - multimedia animation by Yannick Mahe and Bernard Ducommun

Interphase = G1, S, G2

Cell is performing its various metabolic activities

90% of cell cycle time

Mitosis (add to cell cycle diagram)Mitosis Cell Drive Through (1:44)

Mitosis Video (6:11)

• Asexual Cell division• PPMAT• Less than 1 hour

Mitosis: M phase

Mitosis Phases (1:22 fly-through)

• Mitosis Animation scroll to middle of page (nice and slow so you can concentrate on all that is happening)

• Mitosis youtube (2:47)

Plant and Animal Cell Mitosis

• Plant cell mitosis | Flash simulation, Animation, Illustration, Picture, Diagram – eduMedia

• Mitosis | Flash simulation, Animation, Illustration, Picture, Diagram - eduMedia

Can you tell which phase?

Which theory is how the cell cycle works?

Which theory is how the cell cycle works?

Control of the Cell Cycle*

McGraw-Hill animation__control_of_the_cell_cycle.html• Like a control knob of an automatic

washing machine…•

Get analogy handout

Cell Cycle Checkpoints(get out your cell cycle handout)• Cell Cycle Checkpoints (6:13)• Cell cycle checkpoints =

regulatory pathways that control the order and timing (starting/stopping) of cell cycle transitions

• (at G1, G2, M)

Block out

If there is an error at any area, it will be fixed or the cell cycle will stop.

(see analogy handout)Checkpoints: will give the cell a signal to proceed to next phase• G1 Cell growth (big enough? Proteins for

DNA synthesis? Nutrients?) to replication or G0

• G2 DNA synthesis (any DNA repair?) Size?

• M Mitosis (chromosome attachment to spindles)

Write this on Cell Cycle Diagram

• GO• Growth Factors

(GF)• Oncogenes• Cyclins and CDKs

• STOP• Tumor

suppressor genes

• CDK inhibitors

VOCAB WORDS: Growth Factor

• When a cell dies, surrounding cells will send out a chemical (GF) that triggers the start of the cell cycle.

• McGraw-Hill Growth Factors Animation

Dead cells in red

Growth Factor• Protein secreted by body cells to

stimulate other cells to divide

Control of the Cell Cycle• VOCAB WORD: Cyclins - proteins

that start and stop each step of the cell cycle (concentrations change)

• They build up• They break down

Cyclins:

cdk kinases (2:10) You TubeGlobular molecule animation

Cyclin –Cdk –ATP – ball molecules red and teal

Cyclins build and degrade as needed to start and stop the

phases

Cyclin attaches to Cdk

P

Activated by a phosphate

Cyclins build/break-downCdk’s stay in cell

• • phosphate

activates the cdk

P

cdk + cyclin = MPF“maturation promoting factor”

(add to your diagram)

Green cyclin attaches to blue kinase – note phosphate is the site of attachment

Cyclins bind to a Cdk

• Animation of cyclins, cdk's

(shows cdk + cyclin = MPF)

Nobel Prize winner 2001: discovered the key regulators of the cell cycle, cyclin dependent kinase (CDK) and cyclin.

CDK and CYCLINS• Each cyclin-dependent kinase (cdk) forms a

complex with a particular cyclin, a protein that binds and activates the cdk.

• The kinase part of the complex is an enzyme that adds a phosphate (makes the molecule unstable to cause it to be more reactive)

• *The Cell Cycle: Cyclins and Checkpoints

(cyclins and kinases)

• Major control switches of the cell cycle are cyclin-dependent kinases.

Checkpoints: Cyclins and Cdk’s

• Checkpoints in the Cell Cycle Animation• Cyclins, Cdk's, and the Cell Cycle Animation

P53: a “tumor suppressor gene”

• REGULATES THE CELL CYCLE

• Rediscovering Biology - Animation Archive

• p53 can stop and check a damaged DNA strand + repair it

• “the guardian of the genome”

• DNA tube action of p53 (5:18)

Chromosome 17

p53White = p53

common mutation changes arginine 248, colored red here.

DNA is blue and green

Other key sites of mutation are shown in pink, including arginine residues 175, 249, 273 and 282, and glycine 245.

p53 video (p53-DNA complex) (1:32)

How does p53 protect the cells?

• 1. start DNA repair• 2. stop the cell cycle• 3. initiate apoptosis = cell death, if

DNA cannot be repaired• McGraw-Hill Tumor Suppressor Gene

• BIOL 230 Lecture Guide - ADCC Apoptosis by NK Cells (animation)

Apoptosis

• Severe defects in chromosomes block progression through the cell cycle, and can lead to cell suicide, or apoptosis.

• Apoptosis You Tube • Apoptosis Video

What if…• If the cell cycle does not work properly

?• CELL APOPTOSIS=cell death• (A-pop-toe-sis)• Apoptosis (40 secs) by Cancer Quest• Apoptosis Video (1.33 mins)• You Tube Apoptosis Video (4 mins)• THEN GO TO THE CANCER POWER

POINT TO FIND OUT (“cells gone wild”)

p27• p27 is a protein that binds to cyclin and

cdk blocking entry into S phase.

• Recent research (Nature Medicine 3, 152 (1997)) suggests that breast cancer prognosis is determined by p27 levels.

What types of inhibition are these? Competitive or non-

competitive?

OVERVIEW VIDEO

• Bozeman: Cell Cycle, Mitosis, Meiosis (13:39)

Density-dependent inhibition: when crowded cells stop dividing

Cancer cells

• Fail to exhibit density-dependent inhibition

Anchorage Dependence

• Animal cells must be in contact with a solid surface to divide