Cell Division and Mitosis

Definition: Cell division is a fundamental biological process where one cell divides to form two daughter cells.
Key Functions:
- Growth and development
- Tissue renewal
- Reproduction

Bacterial Binary Fission: A form of asexual reproduction in bacteria where a single cell splits into two identical cells.

All cells preparing for division undergo the cell cycle, which includes the following phases:

G1 Phase (Gap 1):
- Cells grow and carry out normal functions.
- Preparation for DNA replication.
S Phase (Synthesis):
- DNA is replicated.
- Each chromosome now consists of two sister chromatids.
- Example: If the cell had 4 chromosomes initially, after S phase, it has 8 sister chromatids.
G2 Phase (Gap 2):
- Further growth and preparation for mitosis.
- Duplicate centrosomes are organized here.

Includes processes of mitosis and cytokinesis.
Mitosis involves several stages:
- Prophase: Chromosomes condense, and the mitotic spindle begins to form.
- Prometaphase: Nuclear envelope breaks down, and spindle fibers attach to chromosomes.
- Metaphase: Chromosomes align in the middle of the cell.
- Anaphase: Sister chromatids are pulled apart toward opposite poles.
- Telophase: Nuclear envelopes reform around chromosomes.
Cytokinesis: The final step where the cytoplasm divides to create two separate cells.
- In animal cells, this is facilitated by a contractile ring made of actin filaments and motor proteins, which help pinch the cell into two.

Centrosome: Acts as the microtubule organizing center (MTOC).
- Duplicates before mitosis to ensure each daughter cell has a centrosome.
Microtubules:
- Structure that connects to chromosomes to facilitate their movement during cell division.