Down’s syndrome in humans is due to

(b): Down’s syndrome is the trisomy of \(21\) stchromosome in man. Down’s syndrome ischaracterized by short stature, warty skin, protrudingtongue, slanting eyes, with folded eyelids. The affectedperson’s face presents a typical mongoloid look. Henceit is also called as mongoloid idiocy. It occurs due tothe phenomenon of nondisjunction.Non disjunction occurs when a pair of homologous chromosomes donot separate in meiosis but migrate to the same poleof the cell resulting in an uneven number ofchromosomes in the daughter cells \((45\) in one and \(47\) in other) This numerical abnormality results in trisomy \((2n + 1)\) and monosomy \((2n -1)\). Nondisjunctionismore common in sex chromosomes.