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: Anatomy
Primordial germ cell is derived from: 
Select and explain. 
A. Ectoderm, B. Mesoderm, C. Endoderm, D. Mesodermal sinus
A: Ectoderm
Answer: A: Ectoderm 
Explanation: A i.e. EctodermPrimordial germ cell develops from epiblast (primitive or primary or embryonic ectoderm)Q at the caudal end of primitive streak in the caudal end of embryo. In the 3rd week, primordial germ cells migrate to a mass of extra embryonic mesoderm and then into the endoderm of yolk sac wall.