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What is the **cell cycle**?
The **cell cycle** is a series of phases that cells go through as they grow and divide. It consists of interphase (G1, S, G2 phases) and the mitotic phase (mitosis and cytokinesis).
Describe the **G1 phase** of the cell cycle.
In the **G1 phase**, the cell grows and performs normal functions. It synthesizes mRNA and proteins necessary for DNA synthesis.
What occurs during the **S phase**?
During the **S phase**, DNA replication occurs, resulting in the duplication of chromosomes to form sister chromatids.
What is the role of the **G2 phase**?
The **G2 phase** is the final preparation phase. The cell continues to grow and produces proteins necessary for mitosis. It also checks for DNA damage.
Define **mitosis**.
**Mitosis** is the process of nuclear division that results in two genetically identical daughter cells. It includes prophase, metaphase, anaphase, and telophase.
What happens during **prophase**?
In **prophase**, chromatin condenses into visible chromosomes, the mitotic spindle forms, and the nuclear envelope begins to disintegrate.
Explain **metaphase**.
During **metaphase**, chromosomes align at the cell's equatorial plate, and spindle fibers attach to the centromeres of the chromosomes.
Describe what occurs in **anaphase**.
In **anaphase**, sister chromatids are pulled apart by the spindle fibers and move towards opposite poles of the cell.
What is **telophase**?
**Telophase** is the stage where the chromosomes arrive at the poles, begin to de-condense into chromatin, and the nuclear envelope reforms around each set of chromosomes.
What is **cytokinesis**?
**Cytokinesis** is the process that divides the cytoplasm of a parental cell into two daughter cells, occurring after mitosis.
How is **cytokinesis** different in plant and animal cells?
In animal cells, **cytokinesis** occurs through the formation of a cleavage furrow. In plant cells, a cell plate forms along the equator of the cell to divide it.
What are **checkpoints** in the cell cycle?
**Checkpoints** are control mechanisms in the cell cycle that ensure the fidelity of cell division. They occur at G1, G2, and M phases.
What is the **G1 checkpoint**?
The **G1 checkpoint** assesses cell size, nutrients, growth factors, and DNA damage before allowing the cell to enter the S phase.
Describe the **G2 checkpoint**.
The **G2 checkpoint** verifies DNA replication completion and checks for DNA damage before the cell enters mitosis.
What is the **M checkpoint** also known as?
The **M checkpoint** is also known as the **spindle assembly checkpoint**, ensuring that all chromosomes are properly attached to the spindle before anaphase.
Define **cancer** in terms of the cell cycle.
**Cancer** is characterized by uncontrolled cell division due to the failure of normal cell cycle regulation, often resulting from mutations in genes that regulate the cell cycle.
What are **oncogenes**?
**Oncogenes** are mutated genes that have the potential to cause cancer by promoting uncontrolled cell proliferation.
What are **tumor suppressor genes**?
**Tumor suppressor genes** are genes that normally prevent uncontrolled cell growth. Mutations in these genes can lead to cancer.
Give an example of a well-known **tumor suppressor gene**.
The **p53 gene** is a well-known tumor suppressor gene that regulates the cell cycle and prevents genome mutation.
What is the role of the **p53 protein**?
The **p53 protein** acts as a transcription factor that regulates the expression of genes involved in cell cycle arrest, DNA repair, and apoptosis.
How do **apoptosis** and the cell cycle relate?
**Apoptosis** is programmed cell death and is a crucial mechanism that eliminates damaged cells that could potentially become cancerous.
What is the **role of cyclins** in the cell cycle?
**Cyclins** are proteins that regulate the progression of cells through the cell cycle by activating cyclin-dependent kinases (CDKs).
Explain how **CDKs** function in cell cycle regulation.
**Cyclin-dependent kinases (CDKs)** are enzymes that, when activated by cyclins, phosphorylate target proteins to regulate cell cycle progression.
What is the **restriction point** in the cell cycle?
The **restriction point** is a critical checkpoint in the G1 phase where the cell becomes committed to entering the S phase and completing the cell cycle.
What are **growth factors** and their role in the cell cycle?
**Growth factors** are external signals that stimulate cell growth and division by triggering specific pathways that advance the cell cycle.
What is **contact inhibition**?
**Contact inhibition** is a regulatory mechanism that stops cells from dividing when they become densely packed, preventing overgrowth of cells.
How does **metastasis** relate to cancer?
**Metastasis** is the spread of cancer cells from the original site to other parts of the body, forming new tumors and complicating treatment.
What is the significance of the **RB protein** in the cell cycle?
The **RB protein** (retinoblastoma protein) regulates the cell cycle by inhibiting the transition from the G1 phase to the S phase until the cell is ready to divide.
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