Question

Down's syndrome is related to

• A. Increase in chromosome number of $21$st pair
• B. Decrease in chromosome number of $21$st pair
• C. Increase in chromosome number of $18$th pair
• D. Decrease in chromosome number of $18$th pair

Answer 1

Answer: (A)

Increase in chromosome number of $21$st pair

Down syndrome is a genetic disorder and the most common autosomal chromosome abnormality in humans, where extra genetic material from chromosome 21 is transferred to a newly formed embryo. These extra genes and DNA cause changes in the development of the embryo and fetus resulting in physical and mental abnormalities.

So, the correct answer is 'Increase in chromosome number of 21st pair'.