How many disease can be identified by karyotyping?
Klinefelters syndrome, phenylketonuria, Thalassemia, Alkaptonuria, Albinism, Colour blindness, Haemophilia, Down syndrome, Turner syndrome

Options

A. 5
B. 4
C. 7
D. 3

Answer

To determine how many diseases can be identified by karyotyping from the given list, we need to analyze each disease based on whether it is associated with chromosomal abnormalities that can be detected through karyotyping.

### Step-by-Step Solution:

1. **Understanding Karyotyping**: Karyotyping is a laboratory technique that allows for the visualization of an individual's chromosomes. It helps in identifying chromosomal abnormalities such as aneuploidy (an abnormal number of chromosomes), deletions, duplications, and structural changes.

2. **List of Diseases**: The diseases mentioned are:
- Klinefelter's syndrome
- Phenylketonuria
- Thalassemia
- Alkaptonuria
- Albinism
- Colour blindness
- Haemophilia
- Down syndrome
- Turner syndrome

3. **Analyzing Each Disease**:
- **Klinefelter's syndrome**: Caused by an extra X chromosome (47,XXY). This is a chromosomal abnormality and can be identified by karyotyping.
- **Phenylketonuria**: A metabolic disorder caused by a mutation in the PAH gene. It does not involve chromosomal abnormalities detectable by karyotyping.
- **Thalassemia**: A blood disorder caused by mutations in the globin genes, not chromosomal number changes. Not detectable by karyotyping.
- **Alkaptonuria**: A metabolic disorder caused by a deficiency of the enzyme homogentisate oxidase. No chromosomal abnormalities are involved.
- **Albinism**: A genetic condition caused by mutations in genes responsible for melanin production. Not detectable by karyotyping.
- **Colour blindness**: A genetic condition typically linked to mutations on the X chromosome. It does not involve chromosomal number changes.
- **Haemophilia**: A genetic disorder caused by mutations in clotting factor genes. No chromosomal abnormalities are involved.
- **Down syndrome**: Caused by an extra copy of chromosome 21 (trisomy 21). This is a chromosomal abnormality and can be identified by karyotyping.
- **Turner syndrome**: Caused by the absence of one X chromosome (45,X). This is a chromosomal abnormality and can be identified by karyotyping.

4. **Identifying Diseases Detected by Karyotyping**: From the analysis, the diseases that can be identified by karyotyping are:
- Klinefelter's syndrome
- Down syndrome
- Turner syndrome

5. **Conclusion**: The total number of diseases that can be identified by karyotyping from the provided list is **3**.

### Final Answer:
**3 diseases can be identified by karyotyping.**

---