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
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