Random change in gene/allelic frequency occurring by chance but not under the control of natural selection is called

Options

A. Genetic drift
B. Natural selection
C. Isolation
D. Adaptive radiation

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the term that describes a random change in gene or allelic frequency that occurs by chance and is not influenced by natural selection.

2. **Identifying Key Concepts**:
- **Gene/Allelic Frequency**: This refers to how often a particular gene or allele appears in a population.
- **Natural Selection**: This is the process where organisms better adapted to their environment tend to survive and produce more offspring, influencing gene frequencies.

3. **Recognizing the Type of Change**: The question specifies that the change in gene frequency is random and not due to natural selection. This indicates that we are looking for a process that occurs by chance.

4. **Defining the Term**: The term that describes this random change in gene or allelic frequency is known as **Genetic Drift**. Genetic drift refers to the changes in allele frequencies in a population due to random sampling of organisms.

5. **Explaining Genetic Drift**:
- Genetic drift can lead to significant changes in a population's genetic makeup over generations.
- It is particularly impactful in small populations where random events can have a larger effect on the overall gene pool.

6. **Conclusion**: Therefore, the correct answer to the question is **Genetic Drift**.