Download Ch7 Cell Cycle

CH 7: CELL CYCLE
PURPOSE OF CELL DIVISION
1.
2.
3.
4.
Growth (if cell’s too big, it splits)
Repair (replace old, injuries)
Regeneration (starfish can make new arm)
Asexual Reproduction (creating new organism)
I. PROKARYOTIC CELL
REPRODUCTION
BINARY FISSION (20MIN)
*DNA is 1 circular molecule
attached to a small
associated protein in the cell
membrane
II. EUKARYOTIC
CELL DIVISION
EUKARYOTIC CELL DIVISION
(PLANTS, ANIMAL, FUNGI, PROTISTS)
DNA:
Linear
 Wrapped around histone proteins
(60% of DNA)
 Chromatin (DNA fiber) Condenses to
form Chromosomes


Step by Step process called Mitosis
EUKARYOTIC CELL CYCLE
Mitosis
Cytokinesis
G1
G2
S
INTERPHASE
 90%
of cell’s life
 Growing & maturing
G1
GAP1
S
Normal functions for that cell
Makes new organelles
*skeletal muscles & nerve cells never leave this phase
(ex. G0)
DNA molecule copies itself into homologous
chromosomes (same shape, diff traits)
Synthesis
G2
GAP2
Proteins for Cell Division are made (Microtubules
Organizing Center, “MTOC”)
CELL DIVISION TIME FRAME: MAMMALIAN CELLS
24 hours total
G1: 12hrs
S: 6hrs
G2: 6 hrs
M: 30min
MITOSIS (NUCLEUS DIVISION)


Not usually finished when
Cytokinesis (cytoplasm
splitting) begins
1 Parent Cell splits into 2
IDENTICAL daughter cells
CHROMATIN
1. PROPHASE

A.
B.
C.
D.
E.
CHROMOSOME
Centromere
Long phase
Chromatin condense to form chromosomes
Nucleoli disappears stops making ribosomes
Nuclear Membrane disappears
MTOC move to opposite ends of the cell and
makes
MTOC organelle called Centrioles makes
microtubules called, Spindle Fibers
Sister
Chromatid
Plant Cell
Prophase
Animal Cell
2. METAPHASE


Centromeres are stabbed by Kinetochore
microtubules (spindle fibers)
Chromsomes line up in the middle (equator)
Metaphase
Plant Cell
Animal Cell
3. ANAPHASE


Sister Chromatids separate and pull towards the ends
“poles” of the cell
Cell stretches out by the elongation of Nonkinetochore
microtubules
Anaphase
Plant Cell
Animal Cell
4. TELOPHASE
Rewinding Prophase
A. Chromosomes unwind into chromatin
B. Microtubules dismantle, Spindle disapears
C. Nucleoli reappear to make ribosomes
D. Nuclear Membrane reforms

Telophase
Plant Cell
Animal Cell
CYTOKINESIS

Begins during Telophase
ANIMALS
• Ring of microfilaments (made
of Actin) wrap around each
other
• Tighten until cells pinch apart
PLANT
• Golgi apparatus begins signals
to create Cell Plate that turns
into a new Cell Wall
REGULATING
CELL CYCLE
CHECK POINTS
1. G0 Checkpoint

Conditions to decide if the cell should divide or not
2. G1 Checkpoint


Cell is adequate size
Chromosomes replicated
DNA errors
3. G2 Checkpoint
DNA Replication, then triggers mitosis
TRIGGERS
1. Cyclin Dependent Kinase (CdK)- enzymes that
catalyze cell division

Phosphorylate proteins
*Cancer Treatment- CdK inhibitor
2. Growth Factors- stimulate cells to divide
Ex. Signaling molecules (hormones), cytokine
OTHER FACTORS THAT INFLUENCE CELL DIVISION:
1.
Density Dependent Inhibition- phenomenon
that animal cells stop dividing when they
come in contact with each other
2.
Anchorage Dependence- requirement that to
divide a cell must be attached to a solid
surface
SEXUAL
REPRODUCTION
SEXUAL REPRODUCTION
 “Meiosis”
mitosis x2
Only occurs in sex organs
Oogenesis: creates egg
 Spermatogenesis: creates sperm
 Sporogenesis: creates pollen

1 parent cell creates 4 genetically different
daughter cells
 Halves the number of Chromosomes

INTERPHASE
Same as Mitosis
 G1, S, G2

1. PROPHASE1
*Major Difference
 Same as Mitosis Prophase, BUT Synapsis occurs

Homologous Chromosomes pair together in Tetrads
 Crossing Over- DNA mixes

Bivalved
Tetrad held together
by protein structure
Crossing Over
2. METAPHASE1

Sister chromatin line up (in tetrads) on equator
3. ANAPHASE1

Tetrads (not sister chromatids) separate in pairs
4. TELOPHASE1

Reverse prophase
CYTOKENESIS
 Create
2 cells, Repeat Meiosis!
 DNA is not doubled before Round 2 of
Meiosis
1. PROPHASE2

Same as Prophase1, but NO SYNAPSIS
2. METAPHASE2

Sister Chromatid line up in separate cells on equator
3. ANAPHASE2

Sister chromatid (in separate) cells separate and
move to poles
4. TELOPHASE2

Undo Prophase, return cell to normal
CYTOKINESIS

4 genetically different daughter cells, with HALF the
normal number of DNA created
DIPLOID
(2n)
Meiosis1
DIPLOID
(2n)
DIPLOID
(2n)
Meiosis2
HAPLOID
(1n)
HAPLOID
(1n)
HAPLOID
(1n)
HAPLOID
(1n)

Somatic Cells- any other cell than a gamete


Gametes- sex cells (egg + sperm)


46 chromosomes
23 chromosomes
Zygote- fertilized egg (egg 23 + sperm 23= 46)
MEIOSIS DIFFERENCES:
Oogenesis
 Only 1 out of the 4 made cells has cytoplasm and organelles
 3 out of 4 are “polar bodies” and die off
Spermatogenesis:
 4 out of 4 made cells turn into sperm