Cell Cycle (final) Flashcards
What are the main phases of the cell cycle? What important events occur during each?
G1:
S:
G2:
Prophase:
Prometaphase:
Metaphase:
Anaphase:
Telophase:
What are cyclins? How are they regulated?
Describe three distinct ways Cdk activity can be regulated?
Compare and contrast the role of p21 and p27 in controlling the cell cycle.
What are mitogens? How do they function?
- Promote production of cyclins that stimulate cell division
What are checkpoints? Where are they located in the cell cycle?
What type of proteins are Rb and p53? How are they similar/different?
Rb protein:
p53:
•
What are two distinct ways the cell can exit the cell cycle? How are they different?
- G0
- Terminally differentiated
?
What are the different types of Cdks?
M-Cdk
G1/S-Cdk
S-Cdk
What is the anaphase-promoting complex (APC/C)?
• Tags cyclins with ubiquitin
Explain what happens during S phase.
• ORC recruits Cdc6
What are three things cells must do in order to divide?
- Duplicate their content (chromosomes, organelles, macromolecules, membrane)
- Partition duplicated contents, grows and split into daughter cells
- cells must grow twice the size (prevents tiny cells) - Coordinate all steps and machinery required for previous two processes
What is the duration of the cell cycle for the following cell types: (1) early fly embryo cells, (2) early frog embryo cells, (3) mammalian intestinal epithelial cells, (4) mammalian fibroblasts in culture
?
The eukaryotic cell cycle usually includes four phases. Why “usually”?
In some organisms early embryonic divisions lack G1 and G2
- Speeds up process
- Consequence: cells shrink by half during each division
What are the three major checkpoints? What is being checked in each?
- G1/S checkpoint:
- G2/M checkpoint:
3.
Explain the G1 Phase
- Period of metabolic activity, DNA repair, and growth
S-Cdk and M-Cdk must be inactivated prior to end of M-phase (and remain stably inactivated in G1). How is this accomplished?
- Eliminating existing cyclins
- Preventing new ones from being synthesized
- Using Cdk inhibitor proteins to prevent any remaining cyclin-CDk from functioning
M-Cdk kinase
Drives entry into mitosis irreversibly
Helps prepare duplicated chromosomes for segregation by promoting condensation
Induces assembly of mitotic spindle
Enhances it’s own activity by shutting down Wee1
Promotes its own inactivation partway through M-phase by activating APC/C, which destroys M cyclin
Describe the activity of Cdc phosphatase in M-phase.
- Activates M-Cdk at end of G2
- Achieved by removing 2 inhibitory phosphatases from M-Cdk
- M-Cdk reinforces its activation by phosphorylating and enhancing Cdc25 activity (positive feedback)
Compare and contrast cohesins and condensin.
Cohesins:
Condensins:
- Promote condensation of chromosomes at beginning of M-phase (allows for easy segregation)
Compare Anaphase A and Anaphase B.
Cytokinesis
