Question

‘Mongoloid idiocy’ occurs due to ______.

विकल्प

• monosomy of sex chromosomes

• monosomy of 21st pair of autosomes

• trisomy of sex chromosomes

• trisomy of 21st pair of autosomes

Answer 1

‘Mongoloid idiocy’ occurs due to trisomy of 21st pair of autosomes.

Explanation:

‘Mongoloid idiocy’ is an outdated term for Down’s syndrome, which is caused by the presence of an extra (third) chromosome 21, hence trisomy 21. This occurs due to non-disjunction during gamete formation, resulting in 47 chromosomes instead of the normal 46. Affected individuals have characteristic physical features and mental retardation associated with this chromosomal abnormality.