This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
The most common chromosomal syndrome is – 
Select and explain. 
A. Fragile X-syndrome, B. Trisomy 17, C. Trisomy 21, D. Trisomy 13
C: Trisomy 21
Answer: C: Trisomy 21 
Explanation: Down syndrome (Trisomy) is the most common of the chromosomal disorder. It occurs in frequency of 1:800 to 1:1000 newborn.