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 will analyze each disease based on whether it is a chromosomal disorder or not.

### Step-by-Step Solution:

1. **Understand Karyotyping**:
- Karyotyping is a laboratory technique that allows for the visualization of chromosomes in a cell. It helps in identifying chromosomal abnormalities, such as aneuploidy (an abnormal number of chromosomes).

2. **Identify the Diseases**:
- The diseases listed are:
- Klinefelter's syndrome
- Phenylketonuria
- Thalassemia
- Alkaptonuria
- Albinism
- Colour blindness
- Haemophilia
- Down syndrome
- Turner syndrome

3. **Classify Each Disease**:
- **Klinefelter's syndrome**: This is a chromosomal disorder (47, XXY). It can be identified by karyotyping.
- **Phenylketonuria**: This is an autosomal recessive disorder and cannot be identified by karyotyping.
- **Thalassemia**: This is also an autosomal recessive disorder and cannot be identified by karyotyping.
- **Alkaptonuria**: This is another autosomal recessive disorder and cannot be identified by karyotyping.
- **Albinism**: This is an autosomal recessive disorder and cannot be identified by karyotyping.
- **Colour blindness**: This is an X-linked recessive disorder and cannot be identified by karyotyping.
- **Haemophilia**: This is also an X-linked recessive disorder and cannot be identified by karyotyping.
- **Down syndrome**: This is a chromosomal disorder (47, +21). It can be identified by karyotyping.
- **Turner syndrome**: This is a chromosomal disorder (45, X). It can be identified by karyotyping.

4. **Count the Chromosomal Disorders**:
- From the analysis, the diseases that can be identified by karyotyping are:
- Klinefelter's syndrome
- Down syndrome
- Turner syndrome
- Therefore, there are **3 diseases** that can be identified by karyotyping.

### Final Answer:
The number of diseases that can be identified by karyotyping is **3**.