- 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).
- Checkpoints between phases of cell cycle.
- G0 (rest) → (is environment favorable?) → S → G2 (is all DNA accurately replicated? is environment favorable?) → Mitosis → (are all chromosomes attached to spindles) → anaphase, cytokinesis
- If checkpoints fail: apoptosis
Tumors happen when:
- Too much cell division, normal apoptosis.
- Normal cell division, not enough apoptosis.