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Questions and Answers
What is the primary role of Maturation Promoting Factor (MPF) in the cell cycle?
What is the primary role of Maturation Promoting Factor (MPF) in the cell cycle?
Which protein interacts with cyclin and CdK to block entry into S phase?
Which protein interacts with cyclin and CdK to block entry into S phase?
What kind of factors can influence the progression of the cell cycle?
What kind of factors can influence the progression of the cell cycle?
Which class of cyclins helps to promote passage through the restriction point in late G1?
Which class of cyclins helps to promote passage through the restriction point in late G1?
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What is a common consequence of a defect in the p53 gene in cancer cells?
What is a common consequence of a defect in the p53 gene in cancer cells?
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Which phase of the eukaryotic cell cycle is the longest?
Which phase of the eukaryotic cell cycle is the longest?
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What is the main function of CDKs in the cell cycle regulation?
What is the main function of CDKs in the cell cycle regulation?
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Which checkpoint is NOT a part of the cell cycle?
Which checkpoint is NOT a part of the cell cycle?
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What is produced during the G2 phase of interphase?
What is produced during the G2 phase of interphase?
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What primarily controls the transitions between different phases of the cell cycle?
What primarily controls the transitions between different phases of the cell cycle?
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Study Notes
The Cell Cycle
- The cell cycle is a series of steps a cell goes through from creation to reproduction
- Prokaryotic cells use binary fission for cell division
- Eukaryotic cells have two main parts in the cell cycle: interphase and mitosis
Interphase
- Interphase is the period between cell divisions
- It is where the cell grows, synthesizes proteins, and performs its normal functions
- There are three main phases of interphase: G1, S, and G2
G1 Phase
- The longest phase of the cell cycle
- The cell grows and synthesizes new proteins and organelles
- During G1, cellular activities are prioritized
S Phase
- Chromosomes are replicated, meaning the DNA is duplicated
- Key proteins required for replication (like centromeres) are made
G2 Phase
- The shortest of the three interphase phases
- The cell produces organelles and molecules necessary for cell division
- This phase is a check-up stage before mitosis
Checkpoints
- A checkpoint is a critical control point in the cell cycle that uses signals to decide whether the cell cycle should continue or stop
- There are three major checkpoints during G1, G2, and M phase
Cell Cycle Regulation
- The cell cycle is regulated by protein kinases, enzymes that control transitions between cell cycle states
- Cyclin-dependent protein kinases (CDKs) are key enzymes in this process
Internal Regulators
- Cyclin-dependent kinases (CDKs) and cyclins are the main regulators of the cell cycle
- Maturation-promoting factor (MPF) consists of CDK and cyclin, and triggers progression through the cell cycle
- P53 is a protein that stops the cell cycle if DNA damage is detected, and can trigger apoptosis (cell death) if the damage is severe
- P27 is a protein that binds to cyclin and CDK to prevent entry into the S phase
G2 Checkpoint
- The G2 Checkpoint is controlled by Maturation Promoting Factor (MPF)
- Active MPF is formed by Mitotic CDK and Mitotic Cyclin
- MPF regulates the transition from G2 to M phase by phosphorylating and activating proteins involved in mitosis
G1 Checkpoint
- The G1 checkpoint is controlled by G1 CDKs and G1 cyclins
- G1 cyclin levels vary throughout the cell cycle
- Additional levels of phosphorylation and dephosphorylation are also involved in regulation
Cyclins
- There are four classes of cyclins:
- G1-cyclins: promote passage through the "Start" point in late G1
- G1/S-cyclins: bind CDKs at the end of G1 and commit the cell to DNA replication
- S-cyclins: bind CDKs during S phase and initiate DNA replication
- M-cyclins: promote the events of mitosis
External Regulators
- External regulators respond to events outside the cell and influence the cell cycle
- They can direct cells to speed up or slow down the cell cycle
- Growth factors are important external regulators, telling cells to speed up division
- Molecules on the surfaces of neighboring cells can act as inhibitors, slowing down or stopping the cell cycle
Uncontrolled Cell Growth
- Cancer cells bypass normal cell cycle regulation, leading to uncontrolled growth
- Over 50% of cancer cells have a defect in the p53 gene
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Description
Explore the fascinating process of the cell cycle, including the phases of interphase. Learn about the G1, S, and G2 phases, their importance, and the role of checkpoints in cell division. This quiz will enhance your understanding of both prokaryotic and eukaryotic cell division.
