Lecture 10: Mitosis, Meiosis and Nondisjunction Study Notes

Cell Cycle Phases:
  - Interphase: Longest phase; includes G1, S, G2.
    - G1: Cell growth, differentiation; checkpoints for size, nutrients, and DNA integrity.
    - S Phase: DNA synthesis; chromosomes replicated to form sister chromatids.
    - G2: Prepares for mitosis; checks for DNA damage.
  - M Phase: Mitosis/cytokinesis; divides into two daughter cells.
Mitosis Overview:
  - Occurs in somatic cells; identical daughter cells (2n).
  - Stages:
    - Prophase: Chromosomes condense; spindle apparatus forms.
    - Metaphase: Chromosomes align at cell equator.
    - Anaphase: Sister chromatids separate.
    - Telophase: Nuclear envelope reforms; cytokinesis follows.
Meiosis Overview:
  - Occurs in germline cells; leads to haploid gametes (n).
  - Stages:
    - Meiosis I: Homologous chromosomes separate (reduction division).
      - Prophase I: Homologous recombination occurs.
    - Meiosis II: Sister chromatids separate.
  - Genetic diversity is achieved through crossover and independent assortment.
Nondisjunction:
  - Failure of chromosomes/sister chromatids to separate during meiosis.
  - Can lead to aneuploidy conditions (e.g., Down syndrome, Turner syndrome).
  - Increased maternal/paternal age correlates with higher risk of nondisjunction.
p53 Role:
- Tumor suppressor; involved in DNA damage response; triggers repair or apoptosis if damage is irreparable.