Question

A human being suffering from Down’s syndrome shows trisomy of 21^st chromosome. Mention the cause of this chromosomal abnormality.

Answer 1

This autosomal abnormality occurs due to the failure of homologous autosomes to separate during gamete formation, a process called non-disjunction. This results in gametes with abnormal chromosome numbers, leading to disorders like Down's syndrome when fertilized by a normal gamete. Thus, the condition arises from non-disjunction of autosomes during meiosis.