A mutation is a change in DNA. If it happens in a gamete-forming cell, it can produce a new allele, and that new allele adds to variation in the next generation.
This lesson is part of variation. It connects to inheritance, where alleles are followed through crosses.
What is the chain from mutation to variation?
Four links take you from a DNA change to a population that varies. Write one sentence for each link.
- A mutation changes the DNA of a gene.
- The changed gene is a new allele.
- If the mutation is in a gamete-forming cell, the allele is passed to offspring.
- The new allele gives a different feature in some individuals, which adds to variation.
Worked example: a mutation in a plant
A gardener finds one red-flowering plant among a bed of white ones. Seeds from the red plant grow into more red-flowering plants.
- A mutation changed a gene for flower colour in a gamete-forming cell of the ancestor.
- The new allele gives red flowers.
- It is inherited, since seeds carry it.
- The bed now has two colours, so variation has increased.
Answer: “A mutation produced a new allele for red flowers. It was passed to the seeds, so the population now shows variation in flower colour.”
Mutation versus environmental change
An environmental change alters one organism only. A mutation in the right cell can be inherited.
| Feature | Mutation in gamete-forming cell | Environmental effect |
|---|---|---|
| Changes DNA | Yes | No |
| Inherited | Yes | No |
| Example | New allele for flower colour | Tanned skin after sunlight |
The mistake that loses marks
The common slip is to say a mutation is only an environmental effect and so cannot be inherited. Some environmental factors raise the chance of a mutation, but the mutation itself is a change in DNA, and it can be passed on if it happens in a gamete-forming cell.
A second slip is to call every mutation harmful. Most have no visible effect, some are harmful, and a few give an advantage in certain conditions.
Check yourself
A student says: “I got a mutation in my skin cells from the sun, so my children will inherit it.” State whether the claim is correct and explain.
Answer
It is not correct. A mutation in a skin cell affects only the body, not the gametes. Only mutations in gamete-forming cells pass to offspring.
What to study next
Check the whole chapter on the variation practice set, then return to interpreting variation distributions for any graph slips.
If a teacher could test each link of the chain with new examples, see online one-to-one Biology tuition.