Question

In Down's syndrome, one extra chromosome is added to

• A. 20${}^{th}$ pair
• B. 21${}^{st}$ pair
• C. 22${}^{th}$ pair
• D. None of the above

Answer 1

Answer: (B)

21${}^{st}$ pair

In Down syndrome, also called as trisomy 21, a child gets an extra chromosome 21 - for a total of 47 chromosomes instead of 46. It is this extra genetic material that causes the physical features and developmental delays associated with DS.