To solve the question about how the frequency of an allele in an isolated population may change, we will analyze the provided options: genetic drift, gene flow, mutation, and natural selection.
### Step-by-Step Solution:
1. **Understanding Genetic Drift**:
- Genetic drift refers to random changes in allele frequencies in a population. This is particularly significant in small, isolated populations where chance events can lead to large changes in allele frequencies over generations.
- Example: In a population of rabbits with brown and white fur, if a random event leads to more brown rabbits surviving and reproducing, the allele for white fur may decrease in frequency or even disappear.
2. **Evaluating Gene Flow**:
- Gene flow, or gene migration, involves the transfer of genetic material between populations through interbreeding. This process generally increases genetic diversity and can counteract the effects of genetic drift.
- Since the question specifies an isolated population, gene flow would not apply here as it implies interaction with another population.
3. **Considering Mutation**:
- Mutation is a change in the DNA sequence that can introduce new alleles into a population. While mutations can affect allele frequencies, they do so on a much smaller scale compared to genetic drift, especially in isolated populations.
- In the context of the question, mutation is not a primary driver of allele frequency change in an isolated population.
4. **Analyzing Natural Selection**:
- Natural selection is the process by which certain traits become more common in a population due to those traits providing a survival or reproductive advantage. While it can change allele frequencies, it typically requires variation in traits that affect fitness.
- In an isolated population, natural selection can occur, but the question specifically asks about the change in allele frequency, making genetic drift a more direct answer.
5. **Conclusion**:
- After evaluating all options, the most relevant mechanism for the change in allele frequency in an isolated population is **genetic drift**. The other options (gene flow, mutation, and natural selection) either do not apply to isolated populations or are less significant in this context.
### Final Answer:
The frequency of an allele in an isolated population may change due to **genetic drift**.
