Cell Cycle and Cell Division

Longest stage of the cell cycle
Cell grows, replicates DNA, and prepares for cell division
Divided into three stages:
1. G1 phase (Gap 1): Cell grows and increases in size
2. S phase (Synthesis): DNA replication occurs
3. G2 phase (Gap 2): Cell prepares for cell division by producing organelles and proteins

Process by which a cell divides into two daughter cells
Types of cell division:
- Mitosis: Somatic cells (non-reproductive cells) divide to produce two identical daughter cells
- Meiosis: Reproductive cells (gametes) divide to produce four non-identical daughter cells with half the number of chromosomes as the parent cell

Consists of four stages:
1. Prophase: Chromatin condenses into visible chromosomes, and the nuclear envelope breaks down
2. Metaphase: Chromosomes align at the center of the cell
3. Anaphase: Sister chromatids separate and move to opposite poles of the cell
4. Telophase: Nuclear envelope reforms, and chromosomes uncoil to form chromatin
Results in two identical daughter cells with the same number of chromosomes as the parent cell

Consists of two consecutive cell divisions (meiosis I and meiosis II)
Meiosis I:
- Prophase I: Homologous chromosomes pair up and exchange genetic material (crossing over)
- Metaphase I: Paired chromosomes align at the center of the cell
- Anaphase I: Homologous chromosomes separate, and each member of the pair moves to opposite poles
- Telophase I: Nuclear envelope reforms, and chromosomes uncoil to form chromatin
Meiosis II:
- Prophase II: Chromosomes condense, and nuclear envelope breaks down
- Metaphase II: Chromosomes align at the center of the cell
- Anaphase II: Sister chromatids separate, and each moves to opposite poles
- Telophase II: Nuclear envelope reforms, and chromosomes uncoil to form chromatin
Results in four non-identical daughter cells with half the number of chromosomes as the parent cell

Mechanisms that ensure the cell cycle progresses correctly
Three main checkpoints:
1. G1 checkpoint: Checks for DNA damage and ensures the cell is ready for DNA replication
2. G2 checkpoint: Checks for DNA damage and ensures the cell is ready for cell division
3. M checkpoint: Checks for proper chromosome alignment and attachment to the spindle fibers during mitosis and meiosis
If a checkpoint detects an error, the cell cycle is halted until the issue is resolved

The cell cycle is a series of events that cells go through as they grow and divide.
It includes Interphase and Cell Division stages.

Represents the longest phase of the cell cycle.
Involves cell growth, DNA replication, and preparation for cell division.
Comprised of three key phases:
- G1 phase (Gap 1): Cell grows and increases in size.
- S phase (Synthesis): DNA is replicated, ensuring each daughter cell receives a complete set of genetic material.
- G2 phase (Gap 2): Cell prepares for division by creating organelles and synthesizing proteins.

The process of a single cell dividing into two daughter cells.
Two main types:
- Mitosis: Occurs in somatic (non-reproductive) cells; produces two genetically identical daughter cells.
- Meiosis: Takes place in reproductive cells (gametes); results in four non-identical daughter cells with half the chromosome count of the parent cell.

Consists of four distinct stages:
- Prophase: Chromatin condenses into visible chromosomes; nuclear envelope disintegrates.
- Metaphase: Chromosomes align at the cell's equatorial plane.
- Anaphase: Sister chromatids are pulled apart to opposite poles of the cell.
- Telophase: Nuclear envelope re-forms; chromosomes de-condense back into chromatin.
Collectively results in two daughter cells with the same chromosome number as the original cell.

Involves two successive cell divisions: meiosis I and meiosis II.
Meiosis I:
- Prophase I: Homologous chromosomes pair and exchange genetic material (crossing over increases genetic diversity).
- Metaphase I: Paired chromosomes align at the center.
- Anaphase I: Homologous chromosomes are separated to opposite poles.
- Telophase I: Nuclear envelope re-forms; chromosomes revert to chromatin.
Meiosis II:
- Prophase II: Chromosomes condense; nuclear envelope disassembles again.
- Metaphase II: Chromosomes align at the center once more.
- Anaphase II: Sister chromatids separate and move to opposite poles.
- Telophase II: Nuclear envelope re-forms; chromatin formation resumes.
Produces four daughter cells, each with half the chromosome count of the parent.

Crucial control mechanisms that oversee the progression of the cell cycle.
Three primary checkpoints:
- G1 checkpoint: Assesses for DNA damage and readiness for DNA replication.
- G2 checkpoint: Checks for DNA damage again and assesses readiness for cell division.
- M checkpoint: Ensures chromosomes are correctly aligned and attached to spindle fibers during division.
If errors are detected, the cycle is paused to allow for repair or correction.