Primitive streak is initiated and maintained by
Ans. is 'a' i.e. Nodal gene "The primitive streak in itself is initiated and maintained by expression of Nodal, a member of the transforming growth factor b (TGFb) family." - Longman's Medical embryology 10/e, p 57
Nodal gene
BMP4
FGF
Brachyury gene
Fertilization and Development of Embryo