This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics And Genetic Disorders, Subject name: Pediatrics
[{'content': 'Most common chromosomal syndrome is: \nSelect and explain. \nA. Fragile X-syndrome, B. Trisomy 17, C. Trisomy 21, D. Trisomy 13', 'role': 'user'}, {'content': "Answer: C \nExplanation: c. Trisomy 21(Ref: Nelson's 20/e p 618-619)Down syndrome (Trisomy 21) is the most common of the chromosomal disorder.Trisomy 16 is the most common trisomy overall, however most do not survive and die in utero Hence, among the live births, or among children, most common chromosomal abnormality is Trisomy 21", 'role': 'assistant'}]