Pick out the correct statements:
(i) Colour blindness is a sex - linkes recessive gene disorder
(ii) Klinefelter's syndrome is `18^(th)` chromosomal trisomy
(iii) Phenylketonuria is an autosomal dominant gene disorder
(iv) Down's syndrome is due to aneuploidy

Options

A. i,ii, and iii are correct
B. i and ii are correct
C. ii, iii and iv are correct
D. i, ii and iv are correct

Answer

To solve the question, we need to evaluate each of the four statements regarding genetic disorders and determine which ones are correct.

### Step-by-Step Solution:

1. **Evaluate Statement (i):**
- "Colour blindness is a sex-linked recessive gene disorder."
- **Explanation:** Colour blindness, particularly red-green colour blindness, is indeed a sex-linked recessive disorder. It is typically carried on the X chromosome, and males are more frequently affected because they have only one X chromosome.
- **Conclusion:** This statement is **correct**.

2. **Evaluate Statement (ii):**
- "Klinefelter's syndrome is 18th chromosomal trisomy."
- **Explanation:** Klinefelter's syndrome is actually caused by the presence of an extra X chromosome in males, resulting in a total of 47 chromosomes (XXY). It is not related to the 18th chromosome but rather to the sex chromosomes.
- **Conclusion:** This statement is **incorrect**.

3. **Evaluate Statement (iii):**
- "Phenylketonuria is an autosomal dominant gene disorder."
- **Explanation:** Phenylketonuria (PKU) is an autosomal recessive disorder. Individuals must inherit two copies of the mutated gene (one from each parent) to express the disorder.
- **Conclusion:** This statement is **incorrect**.

4. **Evaluate Statement (iv):**
- "Down's syndrome is due to aneuploidy."
- **Explanation:** Down's syndrome, also known as Trisomy 21, is indeed caused by aneuploidy, which is the presence of an extra chromosome (in this case, an extra copy of chromosome 21).
- **Conclusion:** This statement is **correct**.

### Final Evaluation:
- The correct statements are:
- (i) Colour blindness is a sex-linked recessive gene disorder. **(Correct)**
- (ii) Klinefelter's syndrome is 18th chromosomal trisomy. **(Incorrect)**
- (iii) Phenylketonuria is an autosomal dominant gene disorder. **(Incorrect)**
- (iv) Down's syndrome is due to aneuploidy. **(Correct)**

Thus, the correct statements are **(i) and (iv)**.