Cell Division Experiment

Cell Division

• Cell division is the process by which cells reproduce, and it differs depending on the type of organism.
• Prokaryotic organisms (such as bacteria) divide by binary fission.
• Unicellular algae (such as dinoflagellates and diatoms) divide with their nuclear envelope intact, with the spindle forming within the nucleus.

Mitosis and Meiosis

• In most eukaryotes, including plants and animals, cell division occurs through mitosis and meiosis.
• Mitosis is the process of cell division that results in two daughter cells with identical genetic material.
• Meiosis is a specialized type of cell division that occurs in germ cells (sex cells) and results in genetically diverse gametes.

Cell Cycle

• The cell cycle is an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division.
• The cell cycle consists of three main stages: interphase, mitotic phase, and cytokinesis.

Interphase

• Interphase is the stage of the cell cycle where the cell grows and prepares for cell division.
• Interphase is divided into three sub-stages: G1, S, and G2.
• G1 (first gap) is the stage where the cell synthesizes enzymes and proteins, and produces cytoplasmic organelles.
• G1/S checkpoint ensures that everything is ready for DNA synthesis.
• S (synthesis) is the stage where DNA replication occurs.
• G2 (second gap) is the stage where the cell grows and prepares for cell division.
• G2 checkpoint ensures that the cell is able to proceed into mitosis.

Mitosis

• Mitosis is the phase of the cell cycle where the chromosomes are evenly divided, producing two daughter cells with identical genetic material.
• There are two types of mitosis: open and closed.
• Open mitosis occurs in most multicellular eukaryotic organisms, where the microtubules invade the nuclear space.
• Closed mitosis occurs in unicellular eukaryotic organisms, where the spindles form inside the nucleus or penetrate the intact nuclear envelope.

Stages of Mitosis

• Prophase:
  • Chromatin fibers become coiled and condensed into discrete chromosomes.
  • Centrosomes polymerize, helping to form the mitotic spindle apparatus.
  • The nuclear envelope disintegrates and disappears.
• Metaphase:
  • Chromosomes become shorter and thicker.
  • Chromosomes align at the metaphase plate (mid-plane) of the cell.
• Anaphase:
  • Shortening of kinetochore microtubules separates the paired sister chromatids.
  • The paired sister chromatids move toward opposite ends of the cell as their kinetochore microtubules shorten.
  • The cell elongates as the non-kinetochore microtubules lengthen and slide over each other at the center of the cell.
• Telophase:
  • The events of prophase are reversed.
  • Nuclei begin to form at opposite poles.
  • The nuclear envelopes of these nuclei form from remnant pieces of the parent cell's nuclear envelope and from pieces of the endomembrane system.
  • Nucleoli reappear.
  • Chromosomes become less condensed.

Cytokinesis

• Cytokinesis is the division of the cell's cytoplasm.
• In animal cells, cytokinesis occurs through cleavage, involving the formation of a cleavage furrow on the surface of the cell.
• In plant cells, cytokinesis occurs through the formation of vesicles derived from the Golgi apparatus, which coalesce to form the cell membrane and deposit cell plate materials.

Meiosis

• Meiosis is a specialized type of cell division that occurs in germ cells (sex cells) and results in genetically diverse gametes.
• Meiosis involves two successive cell divisions: meiosis I and meiosis II.
• During meiosis I, homologous pairs of chromosomes are separated.
• During meiosis II, the sister chromatids of each chromosome are separated.
• Meiosis I prophase involves synapsis and crossing over, which increases genetic variation.
• Meiosis I metaphase involves the alignment of paired homologous chromosomes on the equatorial plate of the cell in a random orientation.
• Meiosis I anaphase involves the separation of homologous pairs, resulting in an independent assortment of chromosomes.
• Meiosis II is similar to mitosis, involving the segregation of sister chromatids.

This quiz is about the process of cell division, including binary fission and the different types of cell division in various organisms such as prokaryotic cells, unicellular algae and diatoms. It covers the concepts of mitosis and meiosis.