Cell Cycle and Cell Division

Cell Cycle

The cell cycle is the sequence of events that occur in a cell as it grows, replicates its DNA, and divides into two daughter cells.

Interphase

• Longest stage of the cell cycle
• Cell grows, replicates its DNA, and prepares for cell division
• Three stages:
  1. G1 phase (Gap 1): Cell grows, increases in size, and prepares for DNA replication
  2. S phase (Synthesis): DNA replication occurs, resulting in two identical copies of DNA
  3. G2 phase (Gap 2): Cell prepares for cell division, organelles and proteins are synthesized

Mitosis

• Process of cell division that results in two daughter cells with the same number of chromosomes as the parent cell
• Four stages:
  1. Prophase: Chromatin condenses into visible chromosomes, nuclear envelope breaks down
  2. Metaphase: Chromosomes line up at the center of the cell, attached to the spindle fibers
  3. Anaphase: Sister chromatids separate, moving to opposite poles of the cell
  4. Telophase: Nuclear envelope reforms, chromosomes uncoil, and nuclei reassemble

Cytokinesis

• Process of cytoplasmic division, resulting in two separate cells
• Occurs after mitosis, and can occur through two mechanisms:
  • Cleavage: In animal cells, the cell membrane pinches inward, dividing the cytoplasm
  • Cell plate formation: In plant cells, a cell plate forms in the center of the cell, dividing the cytoplasm

Meiosis

• Special type of cell division that occurs in reproductive cells (gametes)
• Results in four daughter cells with half the number of chromosomes as the parent cell
• Two successive cell divisions (meiosis I and meiosis II) occur, with a reduction in chromosome number after each division
• Meiosis I:
  • Prophase I: Homologous chromosomes pair up, exchange genetic material (crossing over)
  • Metaphase I: Paired chromosomes line up at the center of the cell
  • Anaphase I: Homologous chromosomes separate, moving to opposite poles
• Meiosis II:
  • Prophase II: Chromosomes condense, nuclear envelope breaks down
  • Metaphase II: Chromosomes line up at the center of the cell
  • Anaphase II: Sister chromatids separate, moving to opposite poles

Understand the different stages of the cell cycle including interphase, mitosis, cytokinesis and meiosis. Learn about the processes of cell growth, DNA replication, and cell division.