5-350 Lecture Notes - Oncogene, Growth Factor, Melanocyte
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28 Jan 2013
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Principles of Development
Spemann grafting experiments -
developmental fate influenced by signals from neighboring cells
"embryonic induction"
INDUCTION
interaction between an inducing tissue that causes a responding tissue
to undergo a change in its direction of differentiation
ex/ vegetal cells induce mesoderm
mesoderm induces neural tissue (Spemann observed)
optic lobe induces optic lens
competence = ability of responding tissue to respond to inducing signal
2 types of induction:
- INSTRUCTIVE induction: inducing signal instructs one path over
another
ex/ ectoderm --> epidermis (no signal)
--> muscle (vegetal cells)
---> nerve (mesoderm)
- PERMISSIVE induction: responding tissue responds to signal non-
specifically (any inductive signal will do)
**instructive inductions occur earlier during development
permissive induction later during development (options narrowed)**
embryonic induction
competence
instructive induction
permissive induction