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 solve the question of selecting the incorrect match from the given options, we will analyze each option step by step.

### Step 1: Analyze the first option - Phenylketonuria and Mental Retardation
- Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in the enzyme that converts phenylalanine to tyrosine.
- The accumulation of phenylalanine and its derivatives can lead to mental retardation.
- Therefore, this match is **correct**.

### Step 2: Analyze the second option - Turner's syndrome and Reduced Chromosome Numbers
- Turner's syndrome is characterized by the presence of only one X chromosome instead of two (XO condition).
- This results in a total of 45 chromosomes instead of the normal 46.
- Thus, this match is **correct**.

### Step 3: Analyze the third option - Klinefelter's syndrome and Sterile Females
- Klinefelter's syndrome occurs in males who have an extra X chromosome (XXY condition).
- Individuals with Klinefelter's syndrome are typically male and exhibit male characteristics, although they may be sterile.
- Therefore, stating that Klinefelter's syndrome results in sterile females is **incorrect**.

### Step 4: Analyze the fourth option - Down syndrome and Physical Characteristics
- Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21).
- Common physical characteristics include a small round head and a furrowed tongue.
- Hence, this match is **correct**.

### Conclusion:
The only incorrect match among the options is the third one, which states that Klinefelter's syndrome results in sterile females. Klinefelter's syndrome affects males, making this statement false.

### Final Answer:
The incorrect match is **Klinefelter's syndrome - Sterile Females**.

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