1. Cellular Reproduction
CHAPTER 14
Cellular Reproduction

2. Overview of the cell cycle
DNA replication
DNA Damage and repair
Nuclear and Cell Division
Regulation of the Cell cycle
Growth Factors and Cell Proliferation
WILL NOT BE
Included in the exam

3. Introduction
Cells reproduce by the process of cell division.
Mitosis leads to cells that are genetically identical to their parent.
Meiosis leads to production of cells with half of the genetic content of the parent.

4. 14.1 The Cell Cycle (1)
The cell cycle is the series of stages that a cell goes through. It consists of the M phase and the interphase.
The M phase includes the process of mitosis and cytokinesis.
Mitosis last about an hour or so.
Interphase constitutes the majority of the cell cycle and lasts longer than the M phase (~23 hrs);
it may extend for days, week, or longer.

5. An overview of the eukaryotic cell cycle

6. The Eukaryotic Cell Cycle
Cell growth === Cell division=== Cell proliferation
-Duplication of DNA
-Replication of DNA
-DNA synthesis
---Mitosis/ Cytokinesis
---Regulation of Cell cycle
Cell cycle
Mitosis ~0.5 hrs
1-Starts—de/condensation- chromatin
2a-sister chromatids
2b-nuclear envelop disorganize
2c-mitotic spindle
3-cytokinesis
G1 8 to 10 hrs
S 6 to 8 hrs
G2 4 to 6 hrs
Go: the cell is out
the cell cycle
Terminal
differentiation Go
-Protein synthesis ?
~23.5 hrs

7. The Cell Cycle (2) Interphase includes G1, S, and G2 periods.
G1 takes place between the end of mitosis and the beginning of DNA replication.
DNA replication occurs during the S phase.
G2 occurs between the end of S and the beginning of mitosis.
Incorporation of 3H-thymidine 3H
1-Add
2-Wash
(Pulse and chase)

8. The Cell Cycle (3) Cell cycles in vivo
Three cell types are distinguished based on their capacity to grow and divide.
Nerve cells have lost the ability to divide.
Liver cells divides in function of stimulus
Stem cells will divide frequently.
Stem cells have asymmetric cell division in which the daughter cells have different fates.

9. The Cell Cycle (4) Control of the Cell Cycle
Cell cycle is focused on initiation of DNA replication and initiation of mitosis.
The cytoplasm contains factors that regulate the state of the nucleus.
The cytoplasm of a replicating cell contains factors that stimulate initiation of DNA synthesis.
The cytoplasm of a cell undergoing mitosis contains factors that trigger chromosomal condensation.

10. The stages of mitosis
in animal and plants
cells

11. The Phases of Mitosis in an Animal Cell
What kind of Signal?
G1 to S
Chromatin begins “condensation
Centrosome duplicates (S phase)

12. The Phases of Mitosis in an Animal Cell
Discrete chromosomes visible under microscope
Nucleus is not clear
Nucleolus ~disappears
Centrosomes move to opposite sides of nucleus
(MTOC, Aster, centrioles)
Mitotic spindle assembles (microtubules)

13. The Phases of Mitosis in an Animal Cell
Prometaphase=Late prophase
Nuclear envelope fragmentation
Centrosomes move to opposite sides of nucleus
Spindle MTs make contact with chromosomes
---centromere
(sequence repeated DNA sequence=heterochromatin
=CEN sequences)
---kinetochore
(protein-like containing structure)

14. Three types of spindle microtubules (MT)
Polar microtubules
Kinetochore microtubules

15. The Phases of Mitosis in an Animal Cell
Perfect and equidistant distribution of the chromosomes.
Metaphase plate
Spindle perturbing drugs arrest cells in metaphase
Colchicine and Nocodazole’s effect

16. Attachment of Chromosomes to the Mitotic Spindle
CEN proteins

17. The Phases of Mitosis in an Animal Cell
Anaphase= separation of sister chromatids
Anaphase A (early)
– chromosomes pulled toward spindle poles
Anaphase B (late)
– poles move away from each other

18. Kinetochore MT= shorter
The Two Types of Movement Involved in Chromosome Separation During Anaphase
Kinetochore MT= shorter
Spindle poles= move away

19. The Phases of Mitosis in an Animal Cell
Reorganization= new cell

20. Microtubule Polarity in the Mitotic Spindle
Polarity of MT

21. Microtubule Polarity in the Mitotic Spindle
Chromosome alignment and separation
Separated by microtubules, also requires additional proteins
like Topoisomerase II, changes in adhesive proteins, (anaphase)
and motor proteins (three different roles--mitotic motors-)

22. Mitotic Motors Kinetochore microtubules Plus & minus ends
Depolymerases binds MT
and induces depolymerization
(chromokinesin, C-terminal and
bipolar kinesin)
Polar microtubules
ATP hydrolysis is require
for MT sliding
(C-terminal and bipolar kinesin)
Astral microtubules
MT associated (cytoplasmic dynein) with cell cortex at plasma membrane (actin microfilaments)
Taxol: it blocks MT
depolymerization

23. Cytokinesis in an Animal Cell
Cleavage furrow associated
with the contractile ring
(Actin and Myosin).
Mechanism: ?
De-phosphorylation and phosphorylation
Rho small GTPases

24. Cytokinesis and Cell Plate Formation in a Plant Cell
Vesicles from Golgi and ER
Youtube====50-year cell division puzzle solved

25. 2 3 1 Typical eukaryotic cell cycle --- G1, S, G2, M
---Control / Regulation Systems:
1--Appropriate time and sequence
of events
2--Each event must be completed
3--Respond to external conditions
(nutrients and growth factors)
Cell cycle control: Key Transition Points in the Cell Cycle
Chromosome segregation 2 3 1

26. Cell Fusion Evidence for the Role of Cytoplasmic Chemical Signals in Cell Cycle Regulation
Specific molecules
present in the cytoplasm
that induce the transformation
from S to G1
(DNA replication
genes=proteins)
from M to G1
(cell cycle regulation
Gene: cdc2=cell division cycle
--regulate the transition from
G2 to M
--cdc2: protein kinase
Regulation by phosphorylation?

27. Experimental demonstration that cells contain factors that stimulate entry into mitosis

28. How is the cell cycle regulated?
Cell Cycle Regulation
Kinase
Phosphatase
Substrate
(P2)
Substrate
(P1)
(Cyclins)
=substrate
(Cyclin-dependent kinase)
-CDK-
Mitotic M-cyclins
Mitotic M-cdks
G1 cyclins
G1 cdks
S cyclins
Cdc2 (Cell Division Cycle ) =kinase
Cdc=cdk

29. Evidence for the Existence of MPF
Maturation promoting factor=MPF
=mitotic cdk-cyclin complex
----control the G2 to M transition

30. Fluctuating Levels of Mitotic Cyclin and MPF During the Cell Cycle
Maximal Enzymatic Activity during the G2-M transition
Substrate:?
Regulation:?
CDK
Relative activity
Mitotic cyclin
CDK

31. mitotic cdk-cyclin complex=MPF
Phosphorylation and Dephosphorylation in the Activation of a Cdk-Cyclin Complex
Ser= variable
Thr= 161
Tyr=15
MPF-i
MPF-a
mitotic cdk-cyclin complex=MPF

32. Fluctuating Levels of Mitotic Cyclin and MPF During the Cell Cycle
Maximal Enzymatic Activity during the G2-M transition
Substrate:?
Regulation:?
Relative activity
CDK

33. The Mitotic Cdk Cycle Cell Cycle Control-I
1-Phosphorylation of lamin in the
nuclear lamina induces depolarization
2-Phosphorylation of condensin induces chromosome condensation
3-Phosphorylation of MT induces
polymerization
4-Phosphorylation of Anaphase
promoting degradation complex.
-APC-(ubiquitin ligase)
Cell Cycle Control-I

34. The Anaphase-Promoting Complex and the Spindle Checkpoint
Mitotic CDK-cyclin
Anaphase promoting complex
(ubiquitin ligase)

35. The Anaphase-Promoting Complex and the Spindle Checkpoint
Regulation of the anaphase promoting complex:
Binding with cdc20
APC cdc20

36. -degradate mitotic cyclins complex
APC cdh1
-degradate mitotic cyclins
complex
SCF
complex
SCF controls G1/S through G2/M transitions
p27 and p21 (cyclin-dependent-kinase inhibitors (CKIs)
G1/S cyclin,
Cyclin E

37. Role of the Rb (Retinoblastoma) Protein in Cell Cycle Control
G1 cdk cyclin
Cell Cycle Control-II

38. How is the cell cycle regulated?
Cell Cycle Regulation
Mitotic M-cyclins
Mitotic M-cdks /A
G1 cyclins
G1 cdks
S cyclins
, 6

39. DNA Damage: p53-dependent and independent pathways
can not be repaired--
Cell Cycle Control-III
ATM kinase=ataxia telangiectasia mutated/mutation
ATM=Ionizing radiation

40. DNA Damage: p53-dependent and independent pathways
ATR= UV radiation
ATR kinase: Inactivation of cyclin

42. Checkpoints=Cell Cycle Control
Spindle checkpoint
Kinetochore attachment
Mad, Bub, Cdc20
DNA replication checkpoint
Completion of DNA synthesis
G2/M transition
Phosphorylation of mitotic cyclin
DNA damage checkpoint
Cell cycle halted at various stages
p53 – guardian of the genome
A. DNA integrity
(DNA damage)
Timer
Cdk
Cyclins
B. Processes
(complete)

43. General Model for Cell Cycle Regulation
APC complex
Regulation
Nutrients
Mitogens
EGF
PDGF
Growth factors
Extra-cellular signals
APC / SCF complex

44. Growth Factor Signaling via the Ras Pathway
-bacteria and yeast cell proliferation/division
Nutrients
Glucose
-mammalian cells cell proliferation/division
Growth factor = mitogens

45. Growth Factor Signaling via the Ras Pathway

46. Growth Factor Signaling via the Ras Pathway
PM or endosomes
Mitogenic
Activated
Protein
Raf=MAPkkk
MEK=MAPkk
ERK=MAPk
Tyrosine
Serine/Threonine

47. The PI3K-Akt Signaling Pathway
Insulin (I) and Insulin-like growth factor (IGF)

48. Cell Growth / Proliferation
EGF/ PDGF TGF-
(+) (-)
Cell Growth / Proliferation
Phosphorylation of Smad
Activation of p27, p21 and p15
(Cdk inhibitors)
MAPK
Mothers Against Decapentaplegic (MAD)
Small Mothers Against paralysis (SMA)

49. General Model for Cell Cycle Regulation
APC complex
Regulation
Nutrients
Mitogens
(+)
(-)
TGF-
EGF
PDGF
(+)
Growth factors
Extra-cellular signals
APC / SCF complex