Download CELL DIVISION

CELL DIVISION
Process by which cells multiply & divide
HOW OFTEN DO CELLS DIVIDE?
• Rate determined by
function & environment
– Skin, blood, digestive
tract divide on regular
basis
– Heart & nerve cells
rarely multiple/divide
after initial formation
REGULATING CELL GROWTH
• Cells grow in number,
NOT in size
– Smaller cells more
efficient
– Easier take in nutrients &
get rid of wastes
• multiply & divide until
they touch one another
– Form solid layer –
division stops
PROBLEMS W/ CELL GROWTH
• Uncontrolled cell
growth
– Cells continue to
multiply & divide even
when touching another
cell
– Form mass of cells/tissue
called tumor
• Cause of Cancer
STRUCTURES
• Chromatin – mass
genetic material
• Chromosome –
X-shaped structure
contains DNA
• Chromatid – each ½ of
chromosome
• Centromere – center
chromosome; holds
chromatids together
STRUCTURES
• Centrioles – proteins in
cytoplasm (form
cytoskeleton)
• Spindle fibers – threads
attach to centromere &
move chromosomes
around the cell
TYPES OF CELL DIVISION
• MITOSIS
– Division of somatic cells
• body cell
• Bone, blood, skin
– Diploid cells (46)
• 2 sets chromosomes
– Produces 2 identical cells
• MEIOSIS
– Division of gametes
• Reproductive cells
• Egg & sperm
– Haploid cells (23)
• 1 set of chromosomes
– Produces 4 different cells
CELL CYCLE
• INTERPHASE
– Longest phase
– Replication occurs
• Chromosomes duplicate
– Appearance
• Chromosomes not visible
• Mass threads called
“chromatin”
MITOSIS
• PROPHASE - (PAIRING)
– Chromosomes pair
– Nuclear membrane
begins to dissolve
MITOSIS
• METAPHASE – (middle)
– Chromosomes lined up
in middle cell
– Nuclear membrane
completely dissolved
MITOSIS
• ANAPHASE – (apart)
– Centromere splits
– Chromosomes move
opposite sides of cell
MITOSIS
• TELOPHASE – (two)
– Cell membrane pinches
together
– Nuclear membrane
returns
• Plants
– Cell wall prevents cell
pinching together
– Form “cell plate”
separates two cells
CELL CYCLE
• CYTOKINESIS
–
–
–
–
Cyto – cytoplasm
Kinesis – movement
“cytoplasm splits”
2 identical copies of
original cell
CELL CYCLE
PLANTS vs. ANIMALS
Interphase
PLANTS vs. ANIMALS
Prophase
PLANTS vs. ANIMALS
Metaphase
PLANTS vs. ANIMALS
Anaphase
PLANTS vs. ANIMALS
Telophase