Multiple choice

Which syndrome is caused by the presence of an extra chromosome?

  1. Stickler syndrome

  2. Klinefelter's syndrome

  3. Turner's syndrome

  4. Down's syndrome
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D Correct answer
Explanation

It results due to the presence of an extra chromosome, No.21. Both the chromosomes of the pair 21 pass into a single egg due to non-disjunction during oogenesis in the mother's ovary. Therefore, the egg contains 24 chromosomes in place of of 23 & the progeny has 47 chromosomes.

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