Expert reviewed • 08 January 2025 • 7 minute read
The significance of a mutation often depends on where it occurs in the body. Somatic mutations arise in non-reproductive cells and affect only the individual in which they occur, while germline mutations appear in reproductive cells and can be passed on to future generations. Understanding the difference is key to appreciating how mutations influence individuals, families, and entire species.
Somatic mutations occur in the body’s ordinary (non-reproductive) cells. They can arise at any point in life, and their effects are often confined to a specific tissue or region of the body. A somatic mutation in a skin cell might affect only a patch of skin, while one in a rapidly dividing bone marrow cell can alter a large population of blood cells.
These mutations do not change the genetic blueprint passed to offspring, meaning their impact is confined to the person affected. Somatic mutations are central to the development of cancer, as multiple mutations in genes such as proto-oncogenes, tumour suppressor genes, and DNA repair genes accumulate over time and transform normal cells into malignant ones.
Cancer connection example:
Germline mutations occur in reproductive cells (sperm or eggs) or their precursors. They can be inherited, ultimately affecting every cell in an offspring’s body. This is like altering the master blueprint, so all future "building plans" carry the change.
Consider the following points regarding germline mutations:
| Feature | Impact | Example |
|---|---|---|
| Inheritance | Passed to offspring | Cystic fibrosis mutation |
| Cell Type | Affects sperm or egg cells | Germline cells |
| Timing | Present from conception | Inherited conditions |
| Evolutionary Influence | Can shape species traits | Subject to natural selection |
Germline mutations underlie well-known genetic conditions such as Huntington’s disease (due to expanded trinucleotide repeats) and haemophilia (an X-linked recessive condition historically noted in European royal families).
The timing of the mutation during development affects how widespread its impact is. Early mutations (in the fertilised egg or the first few dividing cells) can influence a large proportion of the body’s tissues, potentially causing severe conditions or mosaicism. Later mutations tend to be more limited, often restricted to particular cell lineages or organs.
Distinguishing between somatic and germline mutations is crucial in several areas:
As genetic technologies advance, the ability to identify and characterise somatic and germline mutations improves. Techniques like single-cell sequencing, CRISPR gene editing, and liquid biopsies are refining our understanding and guiding personalised medicine, ultimately enhancing our capacity to diagnose, treat, and possibly prevent a range of diseases.