How cells divide and control their genes shapes development. This HL lesson covers D2.1 Cell & nuclear division, D2.2 Gene expression (HL) and D2.3 Water potential.
You will compare mitosis and meiosis, study epigenetic regulation, and use water-potential calculations.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you are ready.
Mitosis: one division giving two genetically identical diploid cells for growth and repair.
Meiosis: two divisions giving four haploid gametes. Variation arises from crossing over and independent assortment. Non-disjunction (failure to separate) can cause conditions such as trisomy 21.
All body cells share the same genome, yet differ because of differential gene expression — only some genes are switched on.
Regulation involves transcription factors and epigenetic marks:
Epigenetic changes alter phenotype without changing the DNA base sequence, and the environment can influence them.
Water potential (Ψ) predicts the direction of osmosis: water moves from higher to lower water potential.
In a hypotonic solution a plant cell becomes turgid; in a hypertonic solution it loses water and may plasmolyse. Animal cells lack a wall, so they can swell and burst or shrink (crenate).
Sort each item into the correct category.
Match each term to its correct description.
D2.1: mitosis (identical diploid) vs meiosis (varied haploid); non-disjunction
D2.2 (HL): differential gene expression; methylation and histone modification
D2.3: Ψ = Ψs + Ψp; osmosis toward lower water potential; turgor and plasmolysis
Skills: water-potential arithmetic; halving of chromosome number in meiosis
Press Finish to see your score.
You have worked through Theme D: Continuity & Change — Cells for IB Diploma Biology. 🎉
Your stars: 0 / 0
Next: test yourself in the Verify stage.