Early Embryonic Development:

  • after 3 cycle the cell is now totipotent - can give rise to any cell type.
  • by 5 days cell is now a blastocyst - a cluster of inner cell mass (which forms the embryo).
  • the outer layer of the blastocyst then forms the placenta.
  • the blastocyst cells are now pluripotent - can give rise to several cell types = human!


  • most of the cells forming the embryo become differentiated - undergone maturation to become distinct in form and function (is now speciaised!).
  • some cells will remian multipotent - can only give rise to limited cell types  e.g. adult stem cells.
  • cell differentiation is irrevirsable in animals but not in plants.

Tissue Culture:

  • plant cells are also totipoetent - produced via tissue culture.
  • involves growing tissues in an artificial medium (which is seperate from the organism).


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