AP Biology — The Cell Cycle & Cancer

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.