The source of all germ cells in the developing embryo is the:
a. yolk sac
b. allantois
c. cytotrophoblast
d. yolk stalk
e. chorion

The correct answer is option A. yolk sac.

Explanation:

Germ cells are cells that have the ability to form or develop gametes. It has half the number of chromosomes. Primordial germ cells present in an embryo are the cells, that in adults produce reproductive gametes.

After 3 weeks of fertilization germ cells are first time become recognizable in humans, in the endodermal layer (which is an inner layer of germ layer) of yolk sac by their huge size and high content of the enzyme alkaline phosphatase.

Thus, the correct answer is option A. yolk sac.

answer:

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