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: Medicine
100% recurrence of disease in Down's syndrome 
Select and explain. 
A. Translocation of 15 + 21 chromsome, B. Mosaic pattern, C. Trisomy - (21, 21 translocation), D. Non Dysjunction
C: Trisomy - (21, 21 translocation)
Answer: C: Trisomy - (21, 21 translocation) 
Explanation: 100% recurrence of disease in Down's syndrome is due to balanced translocation (21 : 21).