The incorrect statement with regard to Haemophilia is

Options

A. It is a dominant disease
B. A single protein involved in the clot- ting of blood is affected
C. It is a sex-linked disease
D. It is a recessive disease

Answer

To solve the question regarding the incorrect statement about Hemophilia, we will analyze each statement related to the condition and determine which one is false.

### Step-by-Step Solution:

1. **Understanding Hemophilia**:
- Hemophilia is a genetic disorder that affects the blood's ability to clot. It is primarily caused by a deficiency in specific clotting factors, namely Factor VIII (Hemophilia A) or Factor IX (Hemophilia B).

2. **Identifying the Type of Disorder**:
- Hemophilia is classified as a sex-linked disorder, specifically located on the X chromosome. This means that the gene responsible for hemophilia is found on the X chromosome.

3. **Recessive Nature**:
- Hemophilia is a recessive disorder. This means that for a male (who has only one X chromosome) to express the disease, he must inherit the affected X chromosome. Females, having two X chromosomes, can be carriers (having one affected X chromosome) without expressing the disease unless both X chromosomes are affected.

4. **Analyzing the Statements**:
- **Statement 1**: "It is a dominant disease."
- This is incorrect because hemophilia is a recessive disorder.
- **Statement 2**: "Single protein involved in the clotting of the blood is affected."
- This is correct as the disorder is due to the deficiency of either Factor VIII or Factor IX.
- **Statement 3**: "It is sex-linked."
- This is correct since the gene for hemophilia is located on the X chromosome.
- **Statement 4**: "It is a recessive disease."
- This is also correct as hemophilia is classified as a recessive disorder.

5. **Conclusion**:
- Based on the analysis, the incorrect statement regarding hemophilia is: **"It is a dominant disease."**

### Final Answer:
The incorrect statement with regard to Hemophilia is: **"It is a dominant disease."**