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44 Cards in this Set

  • Front
  • Back
Regulator of cell cycle in eukaryotic cells
Protein Kinases
-Which are controlled by growth factors
Events during Mitosis
1 hour
Seperation of daughter cells
Cell division (cytokinesis)
Events during Interphase
G1, S, G2
Chromosomes decondense
Nucleus appears uniform
G0
Phase in which cell continues to do normal physiological function but does not divide
Early Embyonic Cells
Cell cycle lasts 30 min or less
NO cell growth
NO G1 and G2 phases
DNA replication is very rapid
Regulation of Cell Cycle
External signals-->growth factors
Internal signals-->cell growth, DNA replication, mitosis
G1
START point is present
Once initiated, there is no turning back
G2
Stimulated by extracellular signals like hormones.
G1 Phase Checkpoint
DNA is repaired before entering the S phase
S Phase Checkpoint
DNA damage is repaired before it is replicated
DNA misincorporation is repaired before it is replicated
G2 Checkpoint
Prevents mitosis if DNA replication is not complete or DNA is damaged
M Phase Checkpoint
Prevents mitosis if the daughter chromosomes are not aligned.
Mechanism of cell cycle arrest
-Sensor protein detect DNA damage
-Senor proteins activate ATM and ATP
-Phosphorylation of Chk 1 & 2 & ATM increase levels of p53 which leads to cell cycle arrest
Role of MPF
Maturation Promoting Factor
Required to transition from G2 to M phase
Cyclin B
A regulatory subunit required for Cdc2 protein kinase activity
P-Thr-161
Required for Cdc2 kinase activity
P-Try-15 & P-Thr-14
Inhibit Cdc2 kinase activity
Activation of MPF is dependent on?
Dephosphorylation of Try-15 and Thr-14
Triggers the degradation of Cyclin B
Activation of Cdc2
Activates transcription of p21
Increase in level of p53
Mechanism of p21
1) Inhibits Cdk/cyclin complexes by binding to them leading to cell cycle arrest
2) Bind to PCNA to inhibit DNA replication
Events in Mitosis
1) Chromosome condensation
2) Formation of mitotic spindle
3) Attachment of chromosomes to spindle
4) Seperation of sister chromatids
5) Formation of daugher nuclei
4 Stages in Mitosis
Prophase
Metaphase
Anaphase
Telophase
Prophase
Beginning-Appearance of condensed chromosomes
End-Breakage of nuclear envelope in higher eukaryotes
Metaphase
Chromosomes align in the center of mitotic spindle
Anaphase
Breakage of the link between the sister chromatids
Telophase
Nuclei reform and chromosomes decondense, cell begins to break apart
Processes which are promoted by activated MPF
Chromatin condensation
Nuclear envelope breakdown
Fragmentation of Golgi and ER
Spindle Formation
Cytokinesis
Completion step of mitosis
Intiated in late anaphase
Triggered by inactivation of MPF
Contraction of actin-myosin filaments
Result of mitosis
Diploid daughter cells
Identical genetic components
Mechanism of p21
1) Inhibits Cdk/cyclin complexes by binding to them leading to cell cycle arrest
2) Bind to PCNA to inhibit DNA replication
Events in Mitosis
1) Chromosome condensation
2) Formation of mitotic spindle
3) Attachment of chromosomes to spindle
4) Seperation of sister chromatids
5) Formation of daugher nuclei
4 Stages in Mitosis
Prophase
Metaphase
Anaphase
Telophase
Prophase
Beginning-Appearance of condensed chromosomes
End-Breakage of nuclear envelope in higher eukaryotes
Metaphase
Chromosomes align in the center of mitotic spindle
Anaphase
Breakage of the link between the sister chromatids
Telophase
Nuclei reform and chromosomes decondense, cell begins to break apart
Processes which are promoted by activated MPF
Chromatin condensation
Nuclear envelope breakdown
Fragmentation of Golgi and ER
Spindle Formation
Cytokinesis
Completion step of mitosis
Intiated in late anaphase
Triggered by inactivation of MPF
Contraction of actin-myosin filaments
Result of mitosis
Diploid daughter cells
Identical genetic components
Result of meiosis
Haploid daughter cells
Half the number of chromosomes
Fertilization
Sperm binds to receptor on surface of egg and fuses with egg plasma membrane-->produces a new diploid cell
Effect of sperm binding to egg on Ca2+ levels
Cytoplasmic Ca2+ levels increase via hydrolysis of PIP2
Effect of increased Ca2+ levels
Exocytosis of secretory vesicles leads to surface alterations and blocks entry of additional sperm