Pick out the correct statements: (i) Hemophilia is a sex – linked recessive disease (ii) Down's syndrome is due to aneuploidy (iii) Phenylketonuria is an autosomal recessive gene disorder (iv) Sickle cell anaemia is an autosomal recessive gene disorder
Answer: (D) (i), (ii) and (iii) are correct. Answer: (D) (i), (ii) and (iii) are correct Solution: Haemophilia is a sex-linked (X-linked) recessive disease (i correct); Down's syndrome is caused by aneuploidy (trisomy of chromosome 21) (ii correct); phenylketonuria is inherited as an autosomal recessive trait (iii correct).
- A.(i) and (iv) are correct
- B.(ii) and (iv) are correct
- C.(i), (iii) and (iv) are correct
- D.(i), (ii) and (iii) are correct✓
Correct Answer
(D) (i), (ii) and (iii) are correct
Solution & Explanation
Answer: (D) (i), (ii) and (iii) are correct Solution: Haemophilia is a sex-linked (X-linked) recessive disease (i correct); Down's syndrome is caused by aneuploidy (trisomy of chromosome 21) (ii correct); phenylketonuria is inherited as an autosomal recessive trait (iii correct). Statement (iv) is also true (sickle-cell anaemia is autosome-linked recessive), so strictly more than one option is defensible; per the official key, option (D) is taken as correct. NCERT Reference: NCERT Class XII, Ch 4, p.75, lines 36-41: "Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s), called aneuploidy. For example, Down’s syndrome results in the gain of extra copy of chromosome 21." and p.75, lines 10-11: "Phenylketonuria : This inborn error of metabolism is also inherited as the autosomal recessive trait."