GCSE Biology · AQA 8461 · Topic 4.1.2
Cell division
Key points
- The nucleus holds chromosomes made of DNA; each carries many genes. Human body cells have 23 pairs.
- In the cell cycle the cell grows, makes more organelles (ribosomes, mitochondria) and copies its DNA; then mitosis separates the chromosomes, and the cytoplasm and membrane divide.
- Mitosis makes two genetically identical daughter cells. It is used for growth, repair and asexual reproduction.
- Stem cells are undifferentiated cells that can become other cell types. Embryonic stem cells can become almost any cell; adult bone marrow stem cells form only some types (e.g. blood cells).
- Plant meristems (in shoot and root tips) keep their stem cells for life and can be used to make clones quickly.
- Stem cells might treat conditions such as diabetes or paralysis, but raise issues: risk of viral infection, ethical and religious objections to using embryos.
- In therapeutic cloning an embryo is made with the patient's own genes, so the stem cells are not rejected.
Topic notesPremium
New cells are needed for growth, repair and, in some organisms, reproduction. This sub-topic explains how a cell copies its genetic material and splits in two, and why unspecialised stem cells are so valuable in medicine and agriculture.
Unlock the full notes with Premium
Premium includes full topic notes, the paper generator, self-quizzes and progress tracking.
Practise this topicPremium
Premium members can generate an exam-style paper with a mark scheme, or take a quick quiz, on Cell division.