Select the chromosomal disorders from the following diseases affecting humans
I. Haemophilia
II. Down's syndrome
III. Klinefelter's syndrome
IV. Sickle cell anemia
V. Turner's syndrome
VI. Thalessemia

Options

A. All except II, III and IV
B. All except I and IV
C. All except I, IV and VI
D. All except I, III and VI

Answer

To determine which of the listed diseases are chromosomal disorders, we will analyze each option one by one:

1. **Haemophilia**:
- Haemophilia is an X-linked recessive disorder caused by a mutation in a gene on the X chromosome. It is classified as a Mendelian disorder, not a chromosomal disorder.
- **Conclusion**: Not a chromosomal disorder.

2. **Down's syndrome**:
- Down's syndrome is caused by trisomy of the 21st chromosome, meaning there is an extra chromosome present. This is a clear chromosomal abnormality.
- **Conclusion**: This is a chromosomal disorder.

3. **Klinefelter's syndrome**:
- Klinefelter's syndrome occurs when males have an extra X chromosome, resulting in a genetic constitution of XXY instead of the normal XY. This is also a chromosomal disorder.
- **Conclusion**: This is a chromosomal disorder.

4. **Sickle cell anemia**:
- Sickle cell anemia is an autosomal recessive disorder caused by a mutation in the gene that codes for the beta chain of hemoglobin. It does not involve a chromosomal abnormality.
- **Conclusion**: Not a chromosomal disorder.

5. **Turner's syndrome**:
- Turner's syndrome occurs when a female is missing one of her X chromosomes, resulting in a genetic constitution of XO. This is a chromosomal disorder.
- **Conclusion**: This is a chromosomal disorder.

6. **Thalassemia**:
- Thalassemia is also an autosomal recessive disorder caused by mutations in the genes responsible for hemoglobin production. It does not involve a chromosomal abnormality.
- **Conclusion**: Not a chromosomal disorder.

### Summary of Findings:
- Chromosomal disorders from the list:
- II. Down's syndrome
- III. Klinefelter's syndrome
- V. Turner's syndrome

### Final Answer:
The chromosomal disorders from the given options are:
- Down's syndrome (II)
- Klinefelter's syndrome (III)
- Turner's syndrome (V)