Cell Cycle Phases

Study Notes

The cell cycle, also known as the cell division cycle, is the process by which a cell grows, replicates its DNA, and divides into two daughter cells.

Phases of the Cell Cycle:

Interphase: The longest phase of the cell cycle, during which the cell grows, replicates its DNA, and prepares for cell division.
- G1 phase (Gap 1): Cell growth and DNA replication.
- S phase (Synthesis): DNA replication occurs.
- G2 phase (Gap 2): Cell prepares for cell division.
Mitosis (M phase): Cell division, where the replicated DNA is divided into two daughter cells.
Cytokinesis: The process of cytoplasmic division, which occurs after mitosis.

There are two main types of cell division:

Occurs in somatic cells (non-reproductive cells).
Results in two daughter cells with the same number of chromosomes as the parent cell.
Consists of four stages:
1. Prophase: Chromatin condenses, and the nuclear envelope breaks down.
2. Metaphase: Chromosomes line up at the center of the cell.
3. Anaphase: Sister chromatids separate and move to opposite poles.
4. Telophase: Nuclear envelope reforms, and chromatin uncoils.

Occurs in reproductive cells (gametes).
Results in four daughter cells with half the number of chromosomes as the parent cell.
Consists of two successive cell divisions:
1. Meiosis I: Reduces the number of chromosomes by half.
2. Meiosis II: Separates the sister chromatids.

Checkpoints: Mechanisms that ensure the cell cycle progresses correctly, preventing errors and ensuring DNA integrity.
Cyclin-dependent kinases (CDKs): Enzymes that regulate the cell cycle by phosphorylating and activating other proteins.
Cyclin: Proteins that bind to and activate CDKs.

Cancer: Uncontrolled cell growth and division due to mutations in genes that regulate the cell cycle.
Apoptosis: Programmed cell death, which can occur if the cell cycle is disrupted or if there are errors in DNA replication.

The cell cycle is the process of cell growth, DNA replication, and cell division into two daughter cells.

Interphase is the longest phase, consisting of:
- G1 phase: Cell growth and DNA replication
- S phase: DNA replication
- G2 phase: Cell preparation for cell division
Mitosis (M phase): Cell division, where replicated DNA is divided into two daughter cells
Cytokinesis: Cytoplasmic division, occurring after mitosis

Occurs in somatic cells (non-reproductive cells)
Results in two daughter cells with the same number of chromosomes as the parent cell
Consists of four stages:
- Prophase: Chromatin condenses, and the nuclear envelope breaks down
- Metaphase: Chromosomes line up at the center of the cell
- Anaphase: Sister chromatids separate and move to opposite poles
- Telophase: Nuclear envelope reforms, and chromatin uncoils

Occurs in reproductive cells (gametes)
Results in four daughter cells with half the number of chromosomes as the parent cell
Consists of two successive cell divisions:
- Meiosis I: Reduces the number of chromosomes by half
- Meiosis II: Separates the sister chromatids

Checkpoints: Mechanisms that ensure the cell cycle progresses correctly
Cyclin-dependent kinases (CDKs): Enzymes that regulate the cell cycle by phosphorylating and activating other proteins
Cyclin: Proteins that bind to and activate CDKs

Cancer: Uncontrolled cell growth and division due to mutations in genes that regulate the cell cycle
Apoptosis: Programmed cell death, occurring if the cell cycle is disrupted or if there are errors in DNA replication