Consequences of mutation in germ cells and somatic cells
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Question
Define a germline mutation.
Answer
A mutation in a **gamete** (egg/sperm) or a gamete-forming cell. It **can be inherited** by offspring.
Question
Define a somatic mutation.
Answer
A mutation in any **body cell other than a gamete-forming cell**. It **cannot be inherited**.
Question
Which type of mutation can be inherited, and why?
Answer
A **germline** mutation — it is in a gamete (or gamete-forming cell), so it is passed to offspring through reproduction.
Question
In which cell would a mutation be heritable?
Answer
A **gamete-forming (germline) cell** — for example a cell in the **testis or ovary**, or a sperm or egg.
Question
What is a mutagen?
Answer
An **agent that increases the rate of mutation** — e.g. UV light, X-rays, or chemicals in tobacco smoke.
Question
Give two examples of mutagens.
Answer
**Radiation** (UV light, X-rays) and **chemicals** (e.g. those in tobacco smoke).
Question
What is a carcinogen?
Answer
A **mutagen that increases the risk of cancer** (for example the chemicals in tobacco smoke).
Question
Define cancer.
Answer
A disease in which body cells **divide uncontrollably**, forming a **tumour** that can invade and spread.
Question
Outline how a mutation can lead to cancer.
Answer
A mutation in a gene controlling **cell division** → the cell **divides uncontrollably** → mutations **accumulate** → a **tumour** forms.
Question
Why does cancer usually need more than one mutation?
Answer
It requires an **accumulation of several mutations** in the same cell line before division becomes fully uncontrolled.
Question
How can smoking cause lung cancer?
Answer
Chemicals in smoke are **mutagens** → they cause **mutations** in lung-cell DNA (cell-division genes) → **uncontrolled division** → a **tumour**.
Question
Is cancer normally inherited?
Answer
**No** — cancer arises from **somatic** mutations in body cells, so it is not passed to offspring (only an inherited *risk* can run in families).
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Topic 4.3 hub
Mutations and gene editing
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