Totipotency and Dedifferentiation

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OUTLINE NOTES
पूर्णशक्तता व विविभेदन (Totipotency and Dedifferentiation):-
पूर्णशक्तता (Totipotency):-
·  Gottlieb Haberlandt ने पूर्णशक्तता की खोज की थी। इन्हें पादप ऊत्तक संवर्धन का जनक भी कहा जाता है।
(Totipotency was discovered by Gottlieb Haberlandt. He is also called as father of plant tissue culture.)
·  परिभाषा (Definition):- 
“एकल पादप कोशिका की सम्पूर्ण पादप के निर्माण की क्षमता को पूर्णशक्तता कहते हैं।”
("The ability of a single plant cell to develop into an entire plant is called totipotency.")
·  सभी या अधिकांश पादप कोशिकाएं पूर्णशक्त होती हैं। एकल पादप कोशिका या कर्तोतक से सम्पूर्ण पादप को विकसित किया जा सकता है।
(All or most of the plant cells are totipotent. The whole plant can be developed from a single plant cell or an explant.)
·  एकल पूर्णशक्त कोशिका से सम्पूर्ण पादप के पुनरुद्धभवन को 2 मुख्य मापदण्ड पूर्ण करने चाहिए –
(Regeneration of the whole plant from a single totipotent cell should fulfill 2 main criteria -)
i. यह एकल कोशिका से प्रारम्भ होना चाहिए क्योंकि पूर्णशक्तता एक कोशिकीय शब्द है।
(It must begin from a single cell because totipotency is a unicellular term.)
ii. यह एकल प्रक्रिया के रूप में पूर्णतया स्वायत होना चाहिए।
(It should be completely autonomous as a single process.)

विविभेदन (Dedifferentiation):-
·   परिभाषा (Definition):- इस प्रक्रिया में परिपक्व व विभेदित कोशिकाएं अपनी पहचान को खो देती हैं तथा आद्य या प्रारम्भिक कोशिकाएं बन जाती हैं और इनमें विभाजन की क्षमता विकसित हो जाती है।
(In this process, mature and differentiated cells lose their identity and become primordial or initial cells and develop the ability to divide.)
·   यह कोशिकाओं की विकासात्मक क्षमता को बढ़ाता है।
(It increases the developmental efficiency of cells.)
·   यह विभेदन का प्रत्यावर्तन (विपरीत प्रक्रिया) होता है इसलिए एक ही कोशिका वंशावली में हो सकता है।
(It is the reversion of differentiation so can occur in the same cell lineage.)
·  जाइगोट में 2 गुण होते हैं –
(Zygote has 2 properties -)
i. उच्च विकासात्मक क्षमता
(High developmental potential)
ii. अच्छी तरह से परिभाषित जीन अभिव्यक्ति पैटर्न
(Well defined gene expression pattern)
अत: जाइगोट को सबसे कम विभेदित या विविभेदित माना जाता है।
(Hence the zygote is considered to be the least differentiated or dedifferentiated.)
·  उसी प्रकार (Similarly):-
Ø  Stem cells कम विभेदित या विविभेदित होती हैं।
(Stem cells are less differentiated or dedifferentiated.)
Ø  कायिक कोशिकाएं अधिक विभेदित होती हैं।
(The somatic cells are more differentiated.)
Ø  इस प्रकार stem cells कायिक कोशिकाओं की तुलना में कम विभेदित होती हैं।
(Thus stem cells are less differentiated than somatic cells.)

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