Sickle cell anaemia is favoured by nature in a malaria - prone area. Which of the following category will be favoured and what type of selection is it?

Options

A. Normal individual , balancing selection
B. Homozygous individual sickle cell, disruptive selection
C. Heterozygous female, balancing selection
D. Homozygous male, normalising selection

Answer

To solve the question regarding sickle cell anemia and its relationship with malaria-prone areas, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Sickle Cell Anemia**:
- Sickle cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene. Individuals with the sickle cell trait (heterozygous) have one normal allele and one sickle cell allele, while homozygous individuals have two sickle cell alleles.

2. **Impact of Malaria**:
- In malaria-prone areas, individuals with the sickle cell trait (heterozygous) have a survival advantage against malaria. This is because the malaria parasite has a harder time surviving in sickle-shaped red blood cells.

3. **Categories of Individuals**:
- **Normal Individuals**: Homozygous for normal hemoglobin (AA).
- **Heterozygous Individuals**: Carriers of the sickle cell trait (AS).
- **Homozygous Sickle Cell Individuals**: Those with sickle cell anemia (SS).

4. **Types of Selection**:
- **Balancing Selection**: This occurs when heterozygous individuals (AS) have a higher fitness than either homozygous type (AA or SS). This type of selection maintains both alleles in the population.
- **Disruptive Selection**: This favors extreme phenotypes over intermediate phenotypes.
- **Normalizing Selection**: This favors average phenotypes and reduces variation.

5. **Evaluating the Options**:
- **Option 1**: Normal individual and balancing selection - Incorrect, as normal individuals do not have the advantage in malaria areas.
- **Option 2**: Homozygous sickle cell and disruptive selection - Incorrect, as homozygous sickle cell individuals have a disadvantage.
- **Option 3**: Heterozygous female and balancing selection - Correct, as heterozygous individuals have a survival advantage in malaria-prone areas.
- **Option 4**: Homozygous male and normalizing selection - Incorrect, as homozygous males do not have an advantage.

6. **Conclusion**:
- The correct answer is **Option 3: Heterozygous female and balancing selection**. This indicates that in malaria-prone areas, heterozygous individuals are favored due to their increased resistance to malaria while avoiding the severe effects of sickle cell anemia.