Medicine

• A gene
  Gene
  A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
  
   expressed by cells in the primitive streak
  Primitive streak
  The primitive streak is a structure that forms during the early stages of avian, reptilian and mammalian embryonic development.-Introduction:...
  
   during germ line development
  Germ line development
  The cells that give rise to the gametes are often set aside during cleavage. During development, these cells will differentiate into primordial germ cells, migrate to the location of the gonad, and form the germ line of the animal....
  
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