Understanding the M Phase of Cell Cycle

May 6, 2024

Mindmap

Lecture Notes on Cell Cycle: M Phase

Overview

In this lecture, we discussed the M phase of the cell cycle, which includes both mitosis and cytokinesis, culminating in the creation of two identical daughter cells from a single original cell.

Review of the Cell Cycle

  • G1, S, and G2 Phases: Together, these make up the interphase.
  • M Phase: Represents cell division, consisting of the division of the nucleus (mitosis) and the division of the cytoplasm (cytokinesis).

Mitosis: Phases and Details

Mitosis is divided into four specific phases: prophase, metaphase, anaphase, and telophase.

Prophase

  • Characteristics:
    • Chromatin condenses into visible chromosomes.
    • Nucleolus disappears.
  • Structural Changes:
    • DNA becomes tightly coiled into sister chromatids.
    • Centromeres attach sister chromatids together.
    • Spindle fibers start forming from centrioles, which move to opposite poles.
    • Nuclear membrane disintegrates.

Metaphase

  • Key Events:
    • Centrioles reach the opposite poles.
    • Spindle fibers align chromosomes along the cell's equator.

Anaphase

  • Description:
    • Spindle fibers pull sister chromatids apart at the centromeres, now termed as individual chromosomes.
    • Chromosomes move towards opposite poles.

Telophase

  • Processes:
    • Nuclear membrane re-forms around each set of chromosomes.
    • Chromosomes loosen into chromatin.
    • The nucleolus becomes visible once more.

Cytokinesis: Division of the Cytoplasm

  • In Animal Cells:
    • The cell membrane pinches inward, eventually dividing into two daughter cells.
  • In Plant Cells:
    • Due to the rigid cell wall, a cell plate forms at the equator and expands outwards to split the cell into two.

Key Points to Remember

  • M Phase: Final and critical phase of the cell cycle, encompassing mitosis and cytokinesis.
  • Mitosis: Involves directional movements of chromosomes and reformation of standard cell nucleus components.
  • Cytokinesis: Finalizes cell division by splitting the cytoplasm into two, using different mechanisms in plant and animal cells.
  • Outcome: Two daughter cells, each genetically identical to the original cell and to each other.

In summary, understanding the mechanism of the M phase is crucial in fields ranging from genetics to medicine, as it underlies fundamental processes of cellular reproduction and regeneration.