BIO 448
MOLECULAR BIOLOGY OF
DIFFERENTIATION
The Role of Formation in Organ Development
• spatial organization of the organism
• linked to morphogenesis
• apoptosis
• cell adhesion
• formation of chemical gradients
• cell movements
Some cells are programmed to die
• apoptosis
• "Death genes“
• ced-3 and ced-4 genes in C. elegans
• ced-9 gene in C. elegans
Some cells are programmed to die
• caspases
• bcl-2 gene
Morphogenes
• provides positional information in the development of animal limbs
• produced in one place, diffused and leads to the conclusion that different cells are exposed to different concentrations of morphogenes and thus develop in different ways, forming a
"concentration gradient".
• concentration gradient of morphogen
• anteroposterior axis
• proximodistal axis
• dorsoventral axis
• polarized activity zone
• polarized activity zone: provides "Positional Information“
• different parts of the limbs develop at specific distances from polarized activity zone.
• Exp: retinoic acid