Barr body is absent in

Options

A. Klinefelter's syndrome
B. Turner's syndrome
C. Normal female
D. Down syndrome in female

Answer

To determine where Barr bodies are absent, we need to understand what a Barr body is and how to calculate its presence based on the number of X chromosomes in an individual.

### Step-by-Step Solution:

1. **Understanding Barr Body**:
- A Barr body is an inactivated X chromosome found in females. In normal females, who have two X chromosomes (XX), one of the X chromosomes is inactivated, resulting in one Barr body.

2. **Calculating Barr Bodies**:
- The formula to calculate the number of Barr bodies is:
\[ \text{Number of Barr bodies} = \text{Number of X chromosomes} - 1 \]

3. **Analyzing Each Condition**:
- **Klinefelter Syndrome (XXY)**:
- Individuals have 2 X chromosomes.
- Calculation: \(2 - 1 = 1\) Barr body.
- **Turner Syndrome (X0)**:
- Individuals have only 1 X chromosome.
- Calculation: \(1 - 1 = 0\) Barr bodies.
- **Normal Female (XX)**:
- Individuals have 2 X chromosomes.
- Calculation: \(2 - 1 = 1\) Barr body.
- **Down Syndrome (XXY)**:
- Individuals have 2 X chromosomes.
- Calculation: \(2 - 1 = 1\) Barr body.

4. **Identifying Where Barr Body is Absent**:
- From the calculations, we see that Barr bodies are absent in Turner Syndrome (0 Barr bodies).

### Conclusion:
The Barr body is absent in Turner syndrome.

### Answer:
Turner syndrome (0 Barr bodies).