How many of the following are Medelian disorders? Haemophilia, Cystic fibrosis, sickle cell anaemia, colour blindness, phenylketonuria, Thalesemia.

Options

A. Three
B. Four
C. Five
D. Six

Answer

To determine how many of the listed disorders are Mendelian disorders, we will analyze each one based on their inheritance patterns.

### Step-by-Step Solution:

1. **Identify the Disorders:**
The disorders listed are:
- Haemophilia
- Cystic Fibrosis
- Sickle Cell Anaemia
- Colour Blindness
- Phenylketonuria (PKU)
- Thalassemia

2. **Analyze Each Disorder:**
- **Haemophilia:**
- Inheritance: X-linked recessive disorder.
- Conclusion: Mendelian disorder.

- **Cystic Fibrosis:**
- Inheritance: Autosomal recessive disorder.
- Conclusion: Mendelian disorder.

- **Sickle Cell Anaemia:**
- Inheritance: Autosomal recessive disorder.
- Conclusion: Mendelian disorder.

- **Colour Blindness:**
- Inheritance: X-linked recessive disorder.
- Conclusion: Mendelian disorder.

- **Phenylketonuria (PKU):**
- Inheritance: Autosomal recessive disorder.
- Conclusion: Mendelian disorder.

- **Thalassemia:**
- Inheritance: Autosomal recessive disorder.
- Conclusion: Mendelian disorder.

3. **Count the Mendelian Disorders:**
All six disorders analyzed (Haemophilia, Cystic Fibrosis, Sickle Cell Anaemia, Colour Blindness, Phenylketonuria, and Thalassemia) are Mendelian disorders.

### Final Answer:
**Total Mendelian Disorders: 6**

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