This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Single Gene Disorders, Subject name: Pathology
List the odd one out among the following 
Select and explain. 
A. Trisomy 18 (Noonan syndrome), B. Trisomy 21 (Downs syndrome), C. Trisomy 18 (Edwards synd.), D. Trisomy 13 (Patau synd.)
A: Trisomy 18 (Noonan syndrome)
Answer: A: Trisomy 18 (Noonan syndrome) 
Explanation: Trisomy 18 is Edward syndrome & not Noonan syndrome. Noonan syndrome occurs in both males and females with a normal karyotype(46,XX and 46,XY). Refer to the image below.