Lecture Notes on Mitosis
Introduction to Mitosis
- Mitosis is the process of cell division occurring throughout the body.
- It is a complex process resulting in two identical cells, each with the organism's genetic information.
- Mitosis is part of the cell cycle, following the copying of the genome and cell preparation.
Phases of Mitosis
Mitosis consists of five phases:
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
Pre-Mitosis
- Occurs in the G2 phase.
- Two chromosome copies are present in the nucleus.
- The centrosome duplicates, resulting in two pairs of centrioles.
Prophase
- Chromatin coils tightly to form recognizable chromosome shapes.
- Sister chromatids are linked by centromere.
- Formation of the mitotic spindle from centrosomes and microtubules.
- Centrosomes pushed apart by growing microtubules.
Prometaphase
- The nucleus disintegrates.
- Microtubules spread to the former nuclear area.
- Attachment of microtubules to kinetochores on chromosomes at the centromeres.
- Organization begins as chromosomes prepare for alignment.
Metaphase
- Centrosomes position at cell poles; asters attach to plasma membrane.
- Chromosomes align along the metaphase plate.
- M checkpoint ensures chromatids are attached to opposite spindle ends.
Anaphase
- Separase enzyme cleaves cohesins, separating sister chromatids.
- Chromatids pulled apart to opposite cell ends by motor proteins and kinetochores.
- Cell elongates as chromatids are pulled apart.
Telophase
- Formation of two nuclei from nuclear fragments.
- Chromosomes begin to uncoil.
- Microtubules disassemble.
- Completion of mitosis with two identical nuclei.
Cytokinesis
- Division of the cytoplasm to form two separate cells.
- Initiated by a cleavage furrow at the metaphase plate.
- Actin microfilaments constrict cell, completing division.
Importance of Mitosis
- Essential for producing new skin, healing wounds, and growth in childhood.
- All somatic cells in the body, except for the first cell (a fertilized egg), arise from mitosis.
- Gametes are produced through a different process known as meiosis.