Variation in gene frequencies within populations can occur by chance rather than by natural selection. This is referred to as

Options

A. Random mating
B. Genetic load
C. Genetic flow
D. Genetic drift

Answer

To solve the question regarding the variation in gene frequencies within populations that occurs by chance rather than by natural selection, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept**: The question is asking about a phenomenon where changes in gene frequencies happen due to random events rather than adaptive processes like natural selection.

**Hint**: Think about how populations can change over time without the influence of environmental pressures.

2. **Identify Key Terms**: The key terms in the question are "gene frequencies," "populations," "chance," and "natural selection."

**Hint**: Focus on the idea of randomness in genetic changes.

3. **Recall Relevant Theories**: Natural selection, as proposed by Charles Darwin, explains how organisms better adapted to their environment tend to survive and reproduce. However, the question specifies a process that is not driven by this selection.

**Hint**: Consider other mechanisms of evolution that do not involve selection pressures.

4. **Consider Examples**: Think about scenarios where random events can affect a population's genetic makeup. For example, a natural disaster could randomly eliminate certain individuals regardless of their genetic traits.

**Hint**: Reflect on how random events can lead to changes in population genetics.

5. **Define the Correct Term**: The term that describes the random changes in gene frequencies due to chance events is known as "genetic drift." This process can lead to significant changes in a population's genetic structure over time.

**Hint**: Remember that "drift" implies a movement or change that is not directed or influenced by selection.

6. **Conclusion**: Therefore, the correct answer to the question is "genetic drift."

### Final Answer:
The variation in gene frequencies within populations that occurs by chance rather than by natural selection is referred to as **genetic drift**.