In the listed Medielian disorders, how many concerned with defective haemoglobin ?
Haemophilia, Cystic fibrosis, Sickel- cell anemia, thalaasemia, Phenylketonuria, Colour- blindness

Options

A. Two
B. One
C. Three
D. Four

Answer

To solve the question of how many Mendelian disorders from the provided list are concerned with defective hemoglobin, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Disorders in the List**: The disorders mentioned are:
- Haemophilia
- Cystic fibrosis
- Sickle-cell anemia
- Thalassemia
- Phenylketonuria
- Colour-blindness

2. **Understand the Role of Hemoglobin**: Hemoglobin is a protein in red blood cells that carries oxygen. Disorders related to hemoglobin will typically affect its structure or function.

3. **Analyze Each Disorder**:
- **Haemophilia**: This is a blood clotting disorder and does not involve hemoglobin.
- **Cystic Fibrosis**: This is a genetic disorder affecting mucus production and does not involve hemoglobin.
- **Sickle-cell Anemia**: This is a disorder where the hemoglobin molecule is defective due to a mutation, leading to sickle-shaped red blood cells. This is directly related to hemoglobin.
- **Thalassemia**: This disorder involves a reduced production of hemoglobin. While it does not produce defective hemoglobin, it is still concerned with hemoglobin levels.
- **Phenylketonuria**: This is a metabolic disorder and does not involve hemoglobin.
- **Colour-blindness**: This is a vision disorder and does not involve hemoglobin.

4. **Count the Relevant Disorders**: From the analysis:
- Sickle-cell anemia (defective hemoglobin)
- Thalassemia (concerned with hemoglobin quantity)

5. **Conclusion**: There are **two disorders** that are concerned with hemoglobin: sickle-cell anemia (defective hemoglobin) and thalassemia (related to hemoglobin quantity).

### Final Answer:
**2 disorders are concerned with defective hemoglobin.**

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