Transcript Cell Division Lifespan of Cells

Cell Division
Lifespan of Cells
Can you guess how often these cells to divide?
Red Blood Cell =
Every 120 days
Stomach Cell =
Every day
Skin Cell =
Every day; new skin each month
Liver Cell =
Every year
Muscle Cell =
Rarely divide; just grows bigger
Nerve Cell =
Rarely divide after birth
Why do cells divide?
To replace dying cells
To pass on genetic material
THINK! – What is our genetic material? DNA
THINK! – How many DNA molecules does a human
body cell have? 46
THINK! – Does every organism have the same number
of DNA molecules? NO
The 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 Cycle
Learning Terminology!
Chromatin
DNA molecules that are loose and thread-like
seen during interphase
HINT – Chromatin is very thin!
Chromosomes
DNA molecules that are tightly coiled up
Seen during mitosis
Duplicated Chromosomes
THINK! – When does each DNA molecule double? Interphase
When DNA doubles each molecule has an identical twin
These twins stay attached at a point called the centromere
Label the Diagram
Chromatin
Chromosome
Duplicated
Chromosome
THINK! – Why would a cell want to coil up its DNA before it divides?
Easier to divide
Interphase
THINK! – What 2 things happen
during interphase?
Cell grows
Cell replicates (doubles) its DNA
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? 6
THINK! – Humans normally have 46 DNA
molecules. How many molecules will each cell
have after mitosis? 46
Phase 1: Prophase
Nickname – “P” for Prepare
Chromatin condenses into chromosomes
Nuclear membrane disappears
Spindle fibers appear
Think of spindle fibers like fishing line. They attach
to the centromere & pull the chromosomes to opposite
ends of the cell.
Phase 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: Anaphase
Nickname – “A” for Apart
Duplicated chromosomes split at the
centromere
Spindle fibers pull the chromosomes to
opposite ends of the cell
Phase 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
Cytokinesis
THINK! – What 2 things happen in
cytokinesis?
Cytoplasm divided between 2 cells
Organelles divided between 2 cells
Cytokinesis: Animal vs. Plant
Cytokinesis in Animal Cells
Cell membrane pinches in to form 2 new cells
Just like pinching in the middle of a water balloon
Cytokinesis in Plant Cells
Cell plate forms in center & new cell wall forms
There is NO pinching inward!
Visualizing Mitosis!
ACTIVITY
INTERACTIVE ACTIVITY TO TRY WITH THE CLASS!
Mitosis Hybrid Medical Animation
http://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 Animations
Glencoe Mitosis Animation
United Streaming (Mitosis_ 1:18)
Real-Time Animations
Animal Cell Mitosis (Just click on “LIVE ANIMAL MITOSIS”)
http://iknow.net/CDROMs/cell_cdrom/index.html
Plant Cell Mitosis (Just click on “PLANT CELL MITOSIS”)
http://iknow.net/CDROMs/cell_cdrom/index.html
Helpful Websites
Cells Alive - http://www.cellsalive.com/mitosis.htm
Biology Corner http://www.biologycorner.com/bio1/cellcycle.html