In which condition the gene ratio remains constant for any species ?

Options

A. Sexual selection
B. Random mating
C. Mutation
D. Gene flow

Answer

**Step-by-Step Solution:**

1. **Understanding Gene Ratio**: The gene ratio refers to the relative frequency of different alleles (gene variants) in a population. It is important to know how various factors can influence these ratios.

2. **Factors Affecting Gene Ratio**: Several factors can change the gene ratio in a population:
- **Mutation**: Changes in the DNA sequence can introduce new alleles, affecting the gene ratio.
- **Gene Migration (Gene Flow)**: Movement of individuals between populations can introduce or remove alleles, altering the gene ratio.
- **Genetic Drift**: Random changes in allele frequencies, especially in small populations, can lead to changes in gene ratios.
- **Natural Selection**: Certain traits may provide a survival advantage, leading to changes in allele frequencies over time.
- **Sexual Selection**: Preferences for certain traits can lead to changes in allele frequencies based on mating choices.

3. **Evaluating the Options**:
- **Sexual Selection**: This does not maintain a constant gene ratio, as it favors certain traits over others.
- **Random Mating**: This is the key factor that maintains a constant gene ratio. In random mating, individuals pair without regard to their genotypes, allowing all alleles an equal chance of being passed on to the next generation.
- **Mutation**: This introduces new alleles, thus changing the gene ratio.
- **Gene Flow**: This involves migration that can alter allele frequencies, hence changing the gene ratio.

4. **Conclusion**: The condition under which the gene ratio remains constant for any species is **random mating**. This ensures that all alleles have an equal opportunity to be represented in the next generation, thereby maintaining the gene ratio.

**Final Answer**: The gene ratio remains constant under the condition of **random mating**.

---