A disease caused by an autosomal primary non-disjunction is :
- Klinefelter's Syndrome
- Down's Syndrome
- Turner's Syndrome
- Sickle Cell Anemia
Answer
(2) Down's Syndrome
Solution
As per NCERT, Down's syndrome is caused by the presence of an additional copy of chromosome number 21 (trisomy of 21) — an autosome.
⇒ Klinefelter's syndrome (44 + XXY) and Turner's syndrome (44 + XO) arise from non-disjunction of sex chromosomes.
⇒ Sickle-cell anaemia is a Mendelian (point mutation) disorder, not a chromosomal one.
∴ Down's syndrome is caused by autosomal non-disjunction.
Answer: (2)