A disease caused by an autosomal primary non-disjunction is
Answer: (A) Down's syndrome. Answer: (A) Down's syndrome Solution: Primary non-disjunction is the failure of chromosomes to separate during meiosis, producing aneuploidy.
- A.Down's syndrome✓
- B.Klinefelter's syndrome
- C.Turner's syndrome
- D.Sickle cell anemia
Correct Answer
(A) Down's syndrome
Solution & Explanation
Answer: (A) Down's syndrome Solution: Primary non-disjunction is the failure of chromosomes to separate during meiosis, producing aneuploidy. Down's syndrome arises from non-disjunction of an autosome (chromosome 21), giving trisomy 21. Klinefelter's and Turner's involve sex-chromosome non-disjunction, and sickle-cell anaemia is a single-gene point mutation, not non-disjunction. NCERT Reference: NCERT Class XII, Ch 4, p.76, lines 19-21: "Down’s Syndrome : The cause of this genetic disorder is the presence of an additional copy of the chromosome number 21 (trisomy of 21)."