Genetic drift can be defined as

Options

A. A random change in gene frequencies of the remaining population, occurring by chance fluctuations
B. A change in an allele due to alteration in the DNA molecule
C. A change in gene frequencies due to exchange of genes between different populations
D. A product of natural selection.

Explanation

**Step-by-Step Solution:**

1. **Understanding Genetic Drift**:
- Genetic drift refers to the changes in the frequency of alleles (gene variants) in a population due to random sampling of organisms. It often occurs in small populations where chance events can have a larger impact on the overall genetic makeup.

2. **Analyzing the Options**:
- **Option A**: "A random change in gene frequency of remaining population occurring by chance fluctuation."
- This option aligns with the definition of genetic drift, as it emphasizes randomness and the effect of chance on gene frequencies.
- **Option B**: "A change in an allele due to alteration in DNA molecule."
- This describes mutations rather than genetic drift.
- **Option C**: "A change in gene frequencies due to the exchange of genes between different populations."
- This refers to gene flow, not genetic drift.
- **Option D**: "A product of natural selection."
- This describes natural selection, which is a different mechanism of evolution.

3. **Selecting the Correct Answer**:
- Based on the definitions and explanations provided, the correct answer is **Option A**: "A random change in gene frequency of remaining population occurring by chance fluctuation."

4. **Conclusion**:
- Genetic drift is characterized by random changes in allele frequencies, particularly in small populations, and is not influenced by natural selection or gene flow.