Lecture on Mitosis

Overview

• Interphase Recap: Before mitosis, cell grows and replicates its DNA.
• Mitosis Defined: Division of a nucleus into two nuclei with identical genetic material.
• Cytokinesis: Follows mitosis, splitting the cytoplasm, forming two separate cells.

Phases of Mitosis

1. Prophase

• Chromosomes condense from chromatin form, visible under a light microscope.
• Chromosomes comprised of two sister chromatids joined at the centromere.
• Nuclear membrane starts to disintegrate.
• Centrosomes migrate to opposite sides of the cell.
• Note: The cell lacks a brain; these processes occur via chemical and thermodynamic reactions.

2. Metaphase

• Nuclear membrane is absent.
• Chromosomes align in the center of the cell.
• Centrosomes at opposite poles of the cell.
• Microtubules extend between centrosomes and centromeres, aiding in chromosome alignment.

3. Anaphase

• Microtubules pull sister chromatids apart.
• Each chromatid becomes an independent chromosome.
• Chromosomes are pulled toward opposite poles of the cell.
• Vocabulary: Kinetochore – part of the structure where microtubules attach during chromatid separation.

4. Telophase

• Chromosomes reach opposite poles.
• Nuclear membranes begin to reform around chromosomes.
• Chromosomes de-condense back into chromatin.
• Cell membrane begins to pinch in preparation for cytokinesis.

Cytokinesis

• Usually considered separate from mitosis, completes division into two cells.
• Occurs alongside the end of mitosis.
• Results in two new cells, each entering interphase to begin the cycle anew.

Additional Notes

• Centrosomes and Centrioles: Centrioles are part of centrosomes, aiding in spindle formation.
• Microtubules: Act as scaffolding, facilitating movement and alignment of chromosomes.

Conclusion

• Mitosis is a complex, well-coordinated process essential for cell division.
• Understanding continues to evolve, with ongoing research into molecular details of how processes are regulated.