cell division Lec 1 Mitosis

Описание: Mitosis is a precise and controlled process ensuring equal distribution of genetic material to daughter cells. It plays a vital role in growth, repair, and maintenance of organisms. Understanding mitosis is essential for studying genetics, development, cancer biology, and biotechnology.
Importance of Mitosis

1. Growth and development of multicellular organisms
2. Replacement of worn-out or damaged cells
3. Healing of wounds
4. Asexual reproduction in some organisms
5. Maintenance of chromosome number (genetic stability)

Cell Cycle Overview

Mitosis occurs as part of the cell cycle, which consists of:
1. Interphase
The preparation phase (not part of mitosis but essential).
It has three stages:

G₁ phase (Gap 1) – Cell growth
S phase (Synthesis) – DNA replication
G₂ phase (Gap 2) – Preparation for mitosis

2. M Phase (Mitotic Phase)
Karyokinesis (nuclear division)
Cytokinesis (cytoplasmic division)
Stages of Mitosis
Mitosis is divided into four main stages:

1. Prophase
Chromatin condenses into visible chromosomes.
Each chromosome consists of two sister chromatids joined at the centromere.
Nuclear membrane starts to disappear.
Spindle fibers begin to form.
2. Metaphase
Chromosomes align at the equatorial plane (metaphase plate).
Spindle fibers attach to centromeres.
3. Anaphase
Centromeres split.
Sister chromatids separate and move toward opposite poles.
4. Telophase
Chromatids reach opposite poles.
Nuclear membrane re-forms.
Chromosomes decondense into chromatin.

Cytokinesis
-After telophase, cytokinesis occurs:
-In animal cells – cleavage furrow formation
-In plant cells – cell plate formation
-This results in two identical daughter cells.