NEET Biology question

Down's syndrome in humans is due to

(A)Three 'X' chromosomes
(B)Three copies of chromosome 21Correct
(C)Monosomy
(D)Two 'Y' chromosomes

Answer: (B)

Solution

Down's syndrome results specifically from trisomy of the autosomal chromosome 21 (three copies instead of two), due to non-disjunction during meiosis. Three X chromosomes (a) describes triple-X syndrome,

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Question ID VK-120196