Germline vs somatic, mutagens & cancer

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A mutation in a **gamete** (egg/sperm) or a gamete-forming cell. It **can be inherited** by offspring.

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A mutation in any **body cell other than a gamete-forming cell**. It **cannot be inherited**.

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A **germline** mutation — it is in a gamete (or gamete-forming cell), so it is passed to offspring through reproduction.

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A **gamete-forming (germline) cell** — for example a cell in the **testis or ovary**, or a sperm or egg.

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An **agent that increases the rate of mutation** — e.g. UV light, X-rays, or chemicals in tobacco smoke.

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**Radiation** (UV light, X-rays) and **chemicals** (e.g. those in tobacco smoke).

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A **mutagen that increases the risk of cancer** (for example the chemicals in tobacco smoke).

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A disease in which body cells **divide uncontrollably**, forming a **tumour** that can invade and spread.

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A mutation in a gene controlling **cell division** → the cell **divides uncontrollably** → mutations **accumulate** → a **tumour** forms.

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It requires an **accumulation of several mutations** in the same cell line before division becomes fully uncontrolled.

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Chemicals in smoke are **mutagens** → they cause **mutations** in lung-cell DNA (cell-division genes) → **uncontrolled division** → a **tumour**.

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**No** — cancer arises from **somatic** mutations in body cells, so it is not passed to offspring (only an inherited *risk* can run in families).