cell division

Overview of Cell Division

  • Focus on processes of mitosis and meiosis

    • Importance and function of cell division types in different cells and situations.

Plant Cell Structure

  • Key components include:

    • Cell Wall: Provides rigidity and structure.

    • Nucleus: Contains DNA in chromatin form.

    • Nucleolus: Found within the nucleus.

    • Vacuole: Storage and maintenance of turgor pressure.

  • Chromatin's role in genetic structure and replication.

Mitosis and its Phases

  • Chromosome Formation:

    • Chromosomes are formed from duplicated DNA, one set from each parent.

    • Key aspect: Chromosome Duplication to ensure identical genetic material.

    • Result: Two identical cells after division.

Prokaryotic Cell Division

  • Prokaryotic cells (e.g., bacteria) divide through Binary Fission:

    • Singular circular DNA replicates at attachment point on plasma membrane.

    • Cell grows, and two DNA molecules become attached to the plasma membrane, moving apart.

    • Plasma membrane constricts inwards, separating cell into two equal-sized cells.

    • Result: Each new cell contains one copy of the genetic material and some cytoplasm.

  • Prokaryotic DNA does not condense during division as seen in eukaryotes.

Eukaryotic Cell Division

  • Eukaryotic cells are larger and more complex, containing multiple DNA molecules organized as chromosomes within a nucleus.

  • Cell Cycle: Consists of:

    • M Phase (Mitotic Phase): Cell division occurs; includes mitosis and cytokinesis.

    • Interphase: Non-dividing phase consisting of G1, S, and G2 phases.

Phases of Interphase

  1. G1 Phase (First Gap):

    • Follows mitosis; longest phase of the cell cycle.

    • Cell grows and prepares for DNA synthesis.

    • Critical decision-making point for the cell to commit to division.

  2. S Phase (Synthesis):

    • Follows G1 and is when DNA replication occurs.

    • Each chromosome duplicates, producing sister chromatids held by a centromere.

  3. G2 Phase (Second Gap):

    • Prepares for mitosis; size continues to increase.

    • Ensures DNA replication is complete and correct.

M Phase Details

  • Mitosis: Active cell division phase when chromosomes condense and nuclear envelope disaggregates.

  • Mitotic Spindle: Made of microtubules, responsible for chromosome movement.

  • Cytokinesis: Occurs late in mitosis, involving the separation of cytoplasmic contents to form two distinct cells.

  • New cell membranes are formed around each daughter cell as the cytoplasm divides.

Summary

  • Mitosis and cytokinesis are crucial for producing identical daughter cells from a single parent cell.

  • The processes of interphase, particularly G1, S, and G2, prepare for effective cell division.