apter 12: The Cell Cycle ow lab – Mitosis only (NOT meiosis – Lab 3) sis lab (Make-up is Thursday 7:30 AM)b in notebooks at end (Have respiration lab finished
Jan 01, 2016
Chapter 12: The Cell Cycle
Tomorrow• Pre-lab – Mitosis only (NOT meiosis – Lab 3)• Mitosis lab (Make-up is Thursday 7:30 AM)b• turn in notebooks at end (Have respiration lab finished!!)
1. When is cell division important?- Reproduction – unicellular organisms – binary fission in bacteria- Growth & development from fertilized egg- Repair (& replacement) of damaged cells
Chapter 12: The Cell Cycle
20 µm100 µm 200 µm
(a) Reproduction. An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism (LM).
(b) Growth and development. This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming two cells (LM).
(c) Tissue renewal. These dividing bone marrow cells (arrow) will give rise to new blood cells (LM).
1. When is cell division important?
2. What is an organism’s genome?- Total hereditary endowment in the cell of a species- Nuclear & extra-nuclear (mito & chloro)
3. How many chromosomes do we have?- 46 – somatic cell (cells of the body)
- 2n - diploid
- 23 – gamete (sex cells – sperm & egg) - n - haploid
4. What are chromosomes made of?- Chromatin- DNA & proteins
Chapter 12: The Cell Cycle
0.5 µm
Chromosomeduplication(including DNA synthesis)
Centromere
Separation of sister
chromatids
Sisterchromatids
Centrometers Sister chromatids
A eukaryotic cell has multiplechromosomes, one of which is
represented here. Before duplication, each chromosome
has a single DNA molecule.
Once duplicated, a chromosomeconsists of two sister chromatids
connected at the centromere. Eachchromatid contains a copy of the
DNA molecule.
Mechanical processes separate the sister chromatids into two chromosomes and distribute
them to two daughter cells.
Fig 12.4 Chromosome duplication & distribution during cell division
INTERPHASE
G1
S(DNA synthesis)
G2
Cytokin
esis
Mito
sisM
ITOTIC
(M) PHASE
1. When is cell division important?
2. What is an organism’s genome?
3. How many chromosomes do we have?
4. What are chromosomes made of?
5. What are the 2 major phases of the cell cycle?- Interphase – 90%- Mitotic phase – 10%
Chapter 12: The Cell Cycle
1. When is cell division important?
2. What is an organism’s genome?
3. How many chromosomes do we have?
4. What are chromosomes made of?
5. What are the 2 major phases of the cell cycle?- Interphase- Mitotic phase
6. What are the steps of the cell cycle?- IPMAT- Interphase- Prophase- Metaphase- Anaphase- Telophase
Chapter 12: The Cell Cycle
G2 OF INTERPHASE PROPHASE PROMETAPHASE
Centrosomes(with centriole pairs) Chromatin
(duplicated)
Early mitoticspindle
Aster
CentromereFragmentsof nuclearenvelope
Kinetochore
Nucleolus Nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Kinetochore microtubule
Nonkinetochoremicrotubules
Combine pro- & prometaphase
Chromosomes appear as Pairs
METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS
Spindle
Metaphaseplate Nucleolus
forming
Cleavagefurrow
Nuclear envelopeformingCentrosome at
one spindle poleDaughter chromosomes
Middle Apart Two
1. When is cell division important?
2. What is an organism’s genome?
3. How many chromosomes do we have?
4. What are chromosomes made of?
5. What are the 2 major phases of the cell cycle?
6. What are the steps of the cell cycle?
7. What is the difference between animal and plant cytokinesis?- Animal – cleavage furrow – cell forms from outside in- Plants – cell plate – cell forms from inside out
Chapter 12: The Cell Cycle
Cleavage furrow
Contractile ring of microfilaments
Daughter cells
100 µm
1 µmVesiclesforming cell plate
Wall of patent cell Cell plate
New cell wall
(a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (SEM)
Figure 12.9 Cytokinesis in animal and plant cells
1. When is cell division important?
2. What is an organism’s genome?
3. How many chromosomes do we have?
4. What are chromosomes made of?
5. What are the 2 major phases of the cell cycle?
6. What are the steps of the cell cycle?
7. What is the difference between animal and plant cytokinesis?
8. How is the cell cycle regulated?- Checkpoints- Make sure cell has enough “ingredients” to move to next stage
Chapter 12: The Cell Cycle
Control system
G2 checkpoint
M checkpoint
G1 checkpoint
G1
S
G2M
Figure 12.14 Mechanical analogy for the cell cycle control system
Figure 12.15 The G1 checkpoint
G1 checkpoint
G1G1
G0
(a) If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.
(b) If a cell does not receive a go-ahead signal at the G1checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state.
Most functioning cells are in G0
1. When is cell division important?
2. What is an organism’s genome?
3. How many chromosomes do we have?
4. What are chromosomes made of?
5. What are the 2 major phases of the cell cycle?
6. What are the steps of the cell cycle?
7. What is the difference between animal and plant cytokinesis?
8. How is the cell cycle regulated?- Checkpoints
- Make sure cell has enough “ingredients” to move to next stage
- Cyclins
- Cyclin-dependent kinase (CDK)
- MPF - maturation promoting factor - Cyclin + CDK = MPF
Chapter 12: The Cell Cycle
Accumulated cyclin moleculescombine with recycled Cdk mol-ecules, producing enough molecules of MPF to pass the G2 checkpoint and initiate the events of mitosis.
MPF promotes mitosis by phosphorylating various proteins. MPF‘s activity peaks during metaphase.
3
During G1, conditions in the cell favor degradation of cyclin, and the Cdk component of MPF is recycled.
5
During anaphase, the cyclin component of MPF is degraded, terminating the M phase. The cell enters the G1 phase.
4
2
Synthesis of cyclin begins in late S phase and continues through G2. Because cyclin is protected from degradation during this stage, it accumulates.
1
Cdk
CdkG2
checkpoint
CyclinMPF
Cyclin is degraded
DegradedCyclin
G 1
G 2
S
M
G1G1 S G2 G2SM M
MPF activity
Cyclin
Time
(a) Fluctuation of MPF activity and cyclin concentration during the cell cycle
(b) Molecular mechanisms that help regulate the cell cycle
Rel
ativ
e C
on
cen
tra
tion
Fig. 12.16 Molecular control of the cell cycle at the G2 checkpoint