October 18th, 2022

Big Bang to Humankind

  • Gene: the basic unit of heredity, at a specific location on a chromosome.
    • Codes for a protein or a segment of a protein.
  • DNA is very compact.
    • DNA wraps around histone proteins.
    • Histones pack on top of themselves to form chromatin.
    • Chromatin coils to make chromosomes.
  • Y chromosome is much smaller than X chromosome and takes less energy to replicate, so we see more males born during times of hardship (like the early Covid pandemic).

Cell Cycle

  • Checkpoints between phases of cell cycle.
    • G0 (rest) β†’ (is environment favorable?) β†’ S β†’ G2 (is all DNA accurately replicated? is environment favorable?) β†’ Mitosis β†’ (are all chromosomes attached to spindles) β†’ anaphase, cytokinesis
    • If checkpoints fail: apoptosis


Tumors happen when:

  1. Too much cell division, normal apoptosis.
  2. Normal cell division, not enough apoptosis.