In a random mating population in equilibrium, which of the following brings about a change in gene frequency in a non-directional manner?

Options

A. Migration
B. Mutation
C. Random drift
D. Selection

Explanation

To solve the question regarding which factor brings about a change in gene frequency in a non-directional manner in a random mating population at equilibrium, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Gene Frequency**:
- Gene frequency refers to how often a particular gene variant (allele) appears in a population. In a population at equilibrium, these frequencies remain constant over generations.

2. **Identify the Factors Affecting Gene Frequency**:
- The options given are migration, mutation, random drift, and selection. Each of these factors can influence gene frequency in different ways.

3. **Analyze Each Option**:
- **Migration**: This involves the movement of individuals into or out of a population, which can change allele frequencies in a directional manner (e.g., introducing new alleles).
- **Mutation**: This is a change in the DNA sequence that can introduce new alleles into a population. Mutations can occur randomly and do not have a specific direction, hence they can be considered non-directional.
- **Random Drift**: This refers to random fluctuations in allele frequencies due to chance events, which can also be non-directional but typically leads to a loss of genetic variation over time.
- **Selection**: Natural selection favors certain alleles over others, leading to directional changes in gene frequencies.

4. **Determine the Correct Answer**:
- Among the options, mutation is the only factor that introduces changes in gene frequency in a non-directional manner. It does not favor one allele over another and can result in various changes without a specific trend.

5. **Conclude**:
- Therefore, the correct answer to the question is **mutation**.

### Final Answer:
- The factor that brings about a change in gene frequency in a non-directional manner in a random mating population at equilibrium is **mutation**.