Select an incorrect match.

Options

A. Phenylketonuria : Mental retardation
B. Turner's syndrome : Reduced number of chromosome
C. Klinefelter's syndrom : Sterile females
D. Down's syndrome : Small round head and furrowed tongue

Answer

To determine the incorrect match from the options provided, let's analyze each one step by step:

1. **Phenylketonuria (PKU) - Mental Retardation**:
- Phenylketonuria is a genetic disorder caused by the deficiency of the enzyme phenylalanine hydroxylase, leading to the accumulation of phenylalanine.
- This condition is indeed associated with mental retardation if not treated early.
- **Conclusion**: This match is correct.

2. **Turner Syndrome - Reduced Number of Chromosomes**:
- Turner syndrome is a chromosomal disorder affecting females, characterized by the absence of one X chromosome (45,X).
- This results in a total of 45 chromosomes instead of the usual 46.
- **Conclusion**: This match is correct.

3. **Klinefelter Syndrome - Sterile Females**:
- Klinefelter syndrome is a genetic condition that occurs in males who have an extra X chromosome (47,XXY).
- This condition leads to sterility in males, not females.
- **Conclusion**: This match is incorrect.

4. **Down Syndrome - Small Round Head and Furrowed Tongue**:
- Down syndrome, or trisomy 21, is characterized by a range of physical and intellectual disabilities, including a small round head and a furrowed tongue.
- **Conclusion**: This match is correct.

Based on the analysis, the incorrect match is **Klinefelter Syndrome - Sterile Females**.

### Summary of the Solution:
- The incorrect match is Klinefelter Syndrome, which is associated with males, not females.