Cell Division

Lifespan of CellsLifespan of Cells

Can you guess how often these cells to divide?

Red Blood Cell =

Stomach Cell =

Skin Cell =

Liver Cell =

Muscle Cell =

Nerve Cell =

Every 120 days

Every day

Every day; new skin each month

Every year

Rarely divide; just grows biggerRarely divide after birth

Why do cells divide?Why do cells divide?To replace dying cells

To pass on genetic material

THINK! – What is our genetic material?

THINK! – How many DNA molecules does a human body cell have?

THINK! – Does every organism have the same number

of DNA molecules?

DNA

46

NO

The Cell CycleThe Cell Cycle

Cell Cycle - the time it takes for a cell to grow & divide

Cell Cycle has 3 stages:

Interphase: time where cell grows bigger & copies or replicates each DNA molecule

Mitosis: time where cell divides out its DNA molecules so each new cell receives the same number

Cytokinesis: time where cell divides its cytoplasm and organelles

Diagram of Cell CycleDiagram of Cell Cycle

Learning Terminology!Learning Terminology!Chromatin

DNA molecules that are loose and thread-likeseen during interphaseHINT – Chromatin is very thin!

ChromosomesDNA molecules that are tightly coiled upSeen during mitosis

Duplicated ChromosomesTHINK! – When does each DNA molecule double?When DNA doubles each molecule has an identical twinThese twins stay attached at a point called the centromere

Interphase

Label the DiagramLabel the Diagram

Chromatin Chromosome DuplicatedChromosome

THINK! – Why would a cell want to coil up its DNA before it divides?Easier to divide

InterphaseInterphase

THINK! – What 2 things happen during interphase?

Cell grows

Cell replicates (doubles) its DNA

Mitosis (4 Phases)Mitosis (4 Phases)

The cell divides the DNA molecules inside its nucleus so that each cell gets the same number of DNA molecules as the original cell

THINK! – A mosquito normally has 6 DNA molecules. How many molecules will each cell have after mitosis?

THINK! – Humans normally have 46 DNA molecules. How many molecules will each cell have after mitosis?

6

46

Phase 1: ProphasePhase 1: Prophase

Nickname – “P” for Prepare

Chromatin condenses into chromosomes

Nuclear membrane disappears

Spindle fibers appearThink of spindle fibers like fishing line. They attach to the centromere & pull the chromosomes to opposite ends of the cell.

Phase 2: MetaphasePhase 2: Metaphase

Nickname – “M” for Middle

Spindle fibers move the duplicated chromosomes into the middle of the cell

THINK! – Why do you think the duplicated chromosomes line up in the middle?

So that the cell can easily check to make sure all the chromosomes are there

Phase 3: AnaphasePhase 3: Anaphase

Nickname – “A” for Apart

Duplicated chromosomes split at the centromere

Spindle fibers pull the chromosomes to opposite ends of the cell

Phase 4: TelophasePhase 4: Telophase

Nickname – “T” for Tear

Chromosomes uncoil back into chromatin

Nuclear Membrane reappears

Spindle fibers disappear

THINK! – Telophase is the complete opposite of what other phase in mitosis? prophase

CytokinesisCytokinesis

THINK! – What 2 things happen in cytokinesis?

Cytoplasm divided between 2 cells

Organelles divided between 2 cells

Cytokinesis: Animal vs. PlantCytokinesis: Animal vs. Plant

Cytokinesis in Animal CellsCell membrane pinches in to form 2 new cellsJust like pinching in the middle of a water balloon

Cytokinesis in Plant CellsCell plate forms in center & new cell wall forms There is NO pinching inward!

Visualizing Mitosis!Visualizing Mitosis!ACTIVITY

INTERACTIVE ACTIVITY TO TRY WITH THE CLASS!

Mitosis Hybrid Medical Animationhttp://hybridmedicalanimation.com/anim_mitosis.html

Mitosis with Music http://www.loci.wisc.edu/outreach/bioclips/CDBio.html

Brain-Pop Clip (Mitosis) http://glencoe.mcgraw-hill.com/sites/007877800x/student_view0/brainpop_movies.html#

Streaming AnimationsGlencoe Mitosis AnimationUnited Streaming (Mitosis_ 1:18)

Real-Time AnimationsAnimal Cell Mitosis (Just click on “LIVE ANIMAL MITOSIS”)

http://iknow.net/CDROMs/cell_cdrom/index.htmlPlant Cell Mitosis (Just click on “PLANT CELL MITOSIS”)

http://iknow.net/CDROMs/cell_cdrom/index.html

Helpful WebsitesCells Alive - http://www.cellsalive.com/mitosis.htmBiology Corner http://www.biologycorner.com/bio1/cellcycle.html