Unit 6
Cell division.
How one cell becomes two: the cell cycle, mitosis and meiosis, stem cells, and cancer, when division loses its controls.
Before this unit
The unit, lesson by lesson
Lessons
5 lessons · 26 practice questions · about 2 hours
The cell cycle
Why cells divide, what a cell does before it divides, how to count chromosomes and chromatids, and why the two daughter cells match the mother cell.
Mitosis step by step
The five phases of mitosis by what you see in the cell: prophase, metaphase, anaphase, telophase and cytokinesis, and how many chromosomes the cell holds in each.
Meiosis
How sex cells are made: two divisions after one copying, homologous pairs that part, four haploid cells, and why no two sex cells are alike.
Stem cells
From fertilised egg to blastocyst: cleavage divisions that do not grow the embryo, the inner cell mass, and totipotent, pluripotent and multipotent stem cells.
When division runs wild
Cancer as cell division that has lost its controls one after another: brakes and accelerators, checkpoints that stop damaged DNA, a lump that recruits blood vessels, and the step that turns a benign tumour malignant.