stem cells

• differentiation 


  process by which unspecialised cells acquire specialised structures or functions
• totipotent


  able to produce any type of body cell
• pluripotent


  can give rise to all of the cell types that make up the body eg embryonic stem cells
• specialised 


  specific roles in the organism of they are part
• multicellular 


  made up of different cell types

  human zygote= 3 cycles= 8 identical cells
• stem cells are unspecialised however can turn into specialised by differentiation
• by 5 days 


  blastocyst formed

  outer layer of placenta forms

  tissue of developing embryo forms
• plant stem cells found in roots and shoots
• hayflick limit 


  number of times cell can divide
• how do stem cells become specialised 


  under a chemical stimulus, genes are activated

  mRNA is transcribed from active genes

  mRNA is transcribed into proteins

  proteins modify the cell to determine the function

  changes to the cell by protein causes it to become specialised
• specialisation happens through differential gene expression