This document discusses several factors involved in embryonic development: induction, competence, and determination. It describes induction as one embryonic tissue transmitting chemical signals that influence another tissue to develop a specific structure. Competence refers to a cell's ability to respond to an inductive signal. Determination occurs when a cell commitment becomes irreversible, unaffected by external influences. The document provides examples of these concepts and discusses the molecular mechanisms underlying cell differentiation during embryonic development.

1. Factors causing
Differentiation -Induction
-Competence
-
Determination
22PZO04
S.KUZHANDAI
RAJ
II MSC

2. INDUCTION :
• Interaction between different types embryonic tissue.
• Morphogenetic effect
• One embryonic tissue transmitted a chemical signals that influence the another embryonic
part to produce a structure.
• Inductor
• Evocator (chemical substance)
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3. Diagrammatic representation :
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Inductor
Responsive
tissue
evocator
organs

4. The blastopore lip is an example for inductor;
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5. Classification of inductor:
I. Based on the inducing ability;
H E AD I N D U C TO R
• Anterior part of archenteron roof
• Archencephalic inductor:
Formation of fore brain , eye , nose .
• Deuterencephalic inductor:
Formation of hind brain and ear
vesicle.
T R U N K I N D U C TO R
• Posterior part of archenteron roof
/gastro coal
• Formation of full digestive system.
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6. Based on interaction :
• Primary inductor: one embryonic tissue interact with the adjacent once and induce
develop into a particular part.
• Secondary inductor: the develop part induce another tissue and induce it to
develop another part
• Tertiary inductor: the develop part produced by the action of secondary induction induce
another tissue to develop into another part.
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7. Example
1. Chorda mesoderm (primary inductor)
2. Ectoderm
3. Neural tube (secondary inductor)
4. Optic vesicle
5. Lense (tertiary inductor)
6. Ectoderm
7. cornea
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8. Chemical based induction
• Inductor act by liberating chemical substance.
• Niv and Twitty (1953) confirmed the idea that inductor act by releasing chemical
substence.
Cultured dorsal lip in media
Dorsal lip remove from media
A piece of ectoderm was introduce into a media
Ectoderm developed into neuron
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9. Mechanism of inducion:
• Gradient theory
• Protein denaturation theory
• One factor hypothesis
• Ionic theory
• Neuro transmitter theory
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10. competence
• In 1940 waddinton introduce concept of competence.
• The ability of cell to respond to a specific inductive signal is called competence.
• Proper growth and differentiation
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11. Example
• Pax 6 gene – eye development in frog,chick,rat,human
• Pax 6 protein – ectoderm competence – optical vesicle
• Pax 6 expression is seen in the head ectoderm which can respond to optic vesicle
formation lenses and it is not seen in other region of the surface ectoderm.
IN RECOMBINANT EXPRIMENT :
Head ectoderm from Pax 6 mutant rat – wild type optic vesicle – no lenses
Head ectoderm from wild type rat – Pax6 mutant optic vesicle - lenses
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12. Pax 6 mutant
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13. Differentiation of embryonic cells
• Embryo continue to develop individual cells continue to differentiate .
• The generation of specialized cell type is called differentiation
• Differentiate cells maintains the identity and property for rest of its life.
• Differentiation through is only the last over stage in a series of event that commit an
undifferentiated cells of an embryo to become a particular cell type.
• Speciation - cell commitment is still lable (capable of being altered) . External
influences matters.
• Determination - cell commitment is now irreversible . External influence does not matter.
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14. Speciation :
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15. Determination
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16. Types of differentiation
• Morphological difference
• Behavioral difference
• Chemical difference
• DIFFERENTIATED CELL VS UNDIFFERENTIATED CELL
• Morphology * chromatin landscape
• Gene expression * Regulator RNA (rRNA)
• Protein related differences
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17. Molecular mechanism of cell differentiation:
strategy I;
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18. Strategy II;
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