Pediatrics General da0d0311 Most common chromosomal syndrome is? A Fragile X-syndrome B Trisomy 17 C Trisomy 21 D Trisomy 13 High-Yield Explanation Ans. is 'c' i.e., Trisomy 21 Down syndrome (Trisomy) is the most common of the chromosomal disorder. It occurs in frequency of 1:800 to 1:1000 newborn.