Equal and unequal cytokinesis at Higher Level: The same statement as SL. The 1A items are the same on both levels; at HL also be ready to explain why every daughter cell needs a mitochondrion.
Practise this as you read
- Identify a cell produced by unequal cytokinesis.
- Explain why each daughter cell needs at least one mitochondrion.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
The big idea: Cytokinesis usually shares the cytoplasm equally, but not always. Whatever the split, each daughter cell needs at least one mitochondrion.
The points to remember
- Equal cytokinesis: two daughter cells of about the same size. This is the usual case.
- Unequal cytokinesis: one daughter cell gets much more cytoplasm than the other.
- Human oogenesis (egg formation): the egg keeps most of the cytoplasm; the polar body gets little.
- Budding in yeast: a small bud grows out of the parent cell and separates.
- Every daughter cell must get at least one mitochondrion, because new mitochondria only come from old ones dividing.
Remember it as: Fair shares usually; the egg and the yeast bud are the exceptions.
Real example: baker's yeast. Baker's yeast, Saccharomyces cerevisiae, reproduces by budding. Each bud leaves a scar on the parent cell's wall, so counting the scars under a microscope shows how many buds a cell has made.
Practice with exam-style questions
Answer exam-style questions and get AI feedback that shows you exactly what examiners want to see in a full-marks response.
Organelles that cannot be made from scratch: A cell cannot build a mitochondrion (or, in plants, a chloroplast) from nothing. New ones form only when existing ones grow and divide, so each daughter cell must inherit at least one.
| Example | What happens | Why it is unequal |
|---|---|---|
| Oogenesis in humans | Meiosis makes one large egg and small polar bodies | The egg stores the cytoplasm and organelles an early embryo needs |
| Budding in yeast | A small bud grows from the parent cell and pinches off | The bud starts small and grows after it separates |
Unequal is not unfair: Even the tiny polar body and the yeast bud each get a nucleus and at least one mitochondrion.
How it is asked: Usually a 1A item: which cell comes from unequal cytokinesis (an egg), or which example is the exception to equal sharing (yeast budding). Sometimes a short written answer on yeast reproduction.
Explain why both daughter cells must receive at least one mitochondrion during cytokinesis, even when the division is unequal.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.