3.6.1Unit 3 — Life on Earth
Mutations
5 min read 5 parts Lesson 29 of 31
Part 1 of 5What Is a Mutation?
Definition
- A mutation is a random change to the genetic material of an organism.
Random
- Mutations happen spontaneously and are not triggered by the needs of the organism or its environment.
Rate increased
- Radiation and some chemicals can increase the rate at which mutations occur.
Example
- A change in a single base in the DNA sequence, such as guanine being swapped for thymine, is a mutation.
Part 2 of 5Effects of Mutations
Effects of Mutations
Neutral
- These have no effect on the chances of survival of the organism.
Advantageous
- These increase the chances of survival, for example by giving better camouflage or resistance to a disease.
Disadvantageous
- These decrease the chances of survival and are less likely to be passed to the next generation.
Outcome depends on environment
- Whether a mutation helps or harms depends on the conditions in which the organism lives.
| Type | Effect on survival |
|---|---|
| Neutral | No effect |
| Advantageous | Increases chance |
| Disadvantageous | Decreases chance |
Part 3 of 5From Mutation to Variation
1
A random change in DNA produces a new allele of a gene.
2
The new allele may change a feature of the organism.
3
Different mutations occur in different individuals, so the population shows variation.
4
If a new allele is advantageous, its owners are better adapted and more likely to survive.
5
Variation makes it possible for a population to change over time as conditions change.
Part 4 of 5Careful Wording
Only source
- Mutation is the only source of new alleles, although alleles can be recombined by other processes.
Not directed
- Mutations occur at random, not in response to a need, so the environment does not cause a helpful mutation.
Population level
- Random mutations that help survival allow the whole population to respond to a changing environment.
Not all harmful
- Many mutations are neutral, so it is wrong to say that all mutations are harmful.
Part 5 of 5Exam Checklist & Tips
3.6.1 – Key Points for the Exam
- Mutation A random change in the genetic material.
- Allele A different version of the same gene.
- Variation Differences between individuals of the same species.
- Advantageous Increasing the chance of survival.
- Spontaneous Happening by chance without an outside trigger.
Common Mistakes
- Writing that mutations happen because an organism needs them; they occur at random.
- Saying all mutations are harmful, when many are neutral and some are advantageous.
- Forgetting that radiation and certain chemicals only increase the rate of mutations, not decide their type.
- Mixing up a gene and an allele; the allele is a version of the gene.