What is the primitive streak?

Answer 1

A primitive streak is an embryology term. It refers to a faint, light streak that can be seen in a blastula and is the first marker of a higher vertebrate. It establishes bilateral symmetry, determines the spot where gastrulation will begin, and also begin germ layer formation. It can be seen on a slide as a distinct line moving inward on the blastula, towards the posterior end.