GCSE Biology · Edexcel 1BI0 · Topic 3E
Variation and mutation
Key points
- Variation can be genetic (e.g. blood group), environmental (e.g. a scar) or a mix of both (e.g. height, body mass).
- Most characteristics are affected by many genes and by the environment, giving continuous variation.
- A mutation is a change in the DNA base sequence. Most have no effect, some alter a protein slightly and a few change it a lot, e.g. changing the shape of an enzyme's active site.
- The Human Genome Project mapped the whole human genome. Benefits: finding genes linked to disease, testing for inherited disorders and personalised medicines.
- Drawbacks: results might cause worry, may be misused by insurers or employers, and having a gene linked to a disease does not mean a person will definitely develop it.
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No two individuals are exactly alike, even identical twins. This sub-topic explains where variation comes from, what mutations are and do, and how mapping the human genome is changing medicine.
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