Select the correct option :-

Options

A. Phenylketonuria is X linked disease and results in accumulation of phenylpyruvic acid.
B. Down’s syndrome is due to triploidy and results in mental retardation
C. Turner’s syndrome is due to trisomy and results in sterile female.
D. Klinefelter’s syndrome is due to extra X-chromosome and results in sterile male.

Answer

To solve the question, we need to analyze each option provided and determine which statement is correct regarding genetic disorders.

### Step-by-Step Solution:

1. **Examine Option A:**
- The statement claims that phenylketonuria (PKU) is an X-linked disease and results in the accumulation of phenylpyruvic acid.
- **Analysis:** Phenylketonuria is actually an autosomal recessive disorder caused by a deficiency of the enzyme phenylalanine hydroxylase, leading to the accumulation of phenylpyruvic acid. Therefore, this statement is incorrect.

2. **Examine Option B:**
- The statement claims that Down syndrome is due to triploidy and results in mental retardation.
- **Analysis:** Down syndrome is caused by trisomy of chromosome 21 (not triploidy, which is having three sets of chromosomes). It typically results in developmental delays and intellectual disabilities. Therefore, this statement is also incorrect.

3. **Examine Option C:**
- The statement claims that Turner syndrome is due to trisomy and results in sterile females.
- **Analysis:** Turner syndrome is actually caused by the absence of one X chromosome (45, X), not by trisomy. Individuals with Turner syndrome are indeed typically sterile, but the cause is not trisomy. Therefore, this statement is incorrect.

4. **Examine Option D:**
- The statement claims that Klinefelter syndrome is due to an extra X chromosome and results in sterile males.
- **Analysis:** Klinefelter syndrome is indeed caused by the presence of an extra X chromosome in males (typically XXY). This condition often leads to sterility and other physical and cognitive issues. Therefore, this statement is correct.

### Conclusion:
The correct option is **D**: Klinefelter syndrome is due to an extra X chromosome and results in sterile males.