Pangenesis


Pangenesis

Pangenesis was Charles Darwin's hypothetical mechanism for heredity. He presented this 'provisional hypothesis' in his 1868 work "The Variation of Animals and Plants Under Domestication" and felt that it brought 'together a multitude of facts which are at present left disconnected by any efficient cause'. The etymology of the word comes from the Greek words "pan" (a prefix meaning "whole", "encompassing") and "genesis" (birth) or "genos" (origin).

Pangenesis holds that body cells shed gemmules, which collect in the reproductive organs prior to fertilization. Thus every cell in the body has a 'vote' in the constitution of the offspring. Atavisms arise due to the awaking of long-dormant gemmules, while limbs regenerate due to the activation of gemmules from the missing limb.

Pangenesis itself is now seen as deeply flawed and not supported by observation, yet it represents Darwin's attempt to explain such diverse phenomena as:
* atavisms,
* the intermediate nature of hybrids (blending inheritance),
* Lamarckian use and disuse, and
* limb regeneration.

Later Elaboration

In his later work, "The Descent of Man", Darwin elaborated further on the model. In a section on the "Laws of inheritance," Darwin specified that two elements in particular were most important: the "transmission" and the "development" of inherited characteristics. Darwin's insights were that characteristics could be transmitted which were not at the time of transmission actually being manifest in the parent organism, and that certain traits would manifest themselves at the same point of development (say, old age) in both the parent and child organisms. In order to make sense of his theory of sexual selection, he also stipulated that certain traits could be passed through organisms but would only develop depending on the sex of the organism in question.

Galton's experiments on rabbits

Darwin's half-cousin Francis Galton conducted wide-ranging inquiries into heredity which led him to refute Charles Darwin's hypothetical theory of pangenesis. In consultation with Darwin, he set out to see if gemmules were transported in the blood. In a long series of experiments in 1869 to 1871, he transfused the blood between dissimilar breeds of rabbits, and examined the features of their offspring [http://www.abc.net.au/rn/science/ss/stories/s216074.htm] . He found no evidence of characters transmitted in the transfused blood Harv | Bulmer | 2003 | pp=116-118. Darwin challenged the validity of Galton's experiment, giving his reasons in an article published in 'Nature' [http://darwin-online.org.uk/content/frameset?itemID=F1751&viewtype=side&pageseq=1] where he wrote: "Now, in the chapter on Pangenesis in my "Variation of Animals and Plants under Domestication," I have not said one word about the blood, or about any fluid proper to any circulating system. It is, indeed, obvious that the presence of gemmules in the blood can form no necessary part of my hypothesis; for I refer in illustration of it to the lowest animals, such as the Protozoa, which do not possess blood or any vessels; and I refer to plants in which the fluid, when present in the vessels, cannot be considered as true blood." He goes on to admit: "Nevertheless, when I first heard of Mr. Galton's experiments, I did not sufficiently reflect on the subject, and saw not the difficulty of believing in the presence of gemmules in the blood."

External links

* [http://www.esp.org/books/darwin/variation/facsimile/title3.html On-line Facsimile Edition of "The Variation of Animals and Plants Under Domestication"] from Electronic Scholarly Publishing

* [http://darwin-online.org.uk/EditorialIntroductions/Freeman_VariationunderDomestication.html Variation under Domestication] , From: Freeman, R. B. 1977. "The Works of Charles Darwin: An Annotated Bibliographical Handlist". 2nd edn. Dawson: Folkstone, at DarwinOnline, with links to online versions of the 1st. edition, first and second issues, and the 2nd. edition.

ee also

*Lamarckism


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Pangénesis — Saltar a navegación, búsqueda La pangénesis es la teoría defendida por Anaxágoras, Demócrito y los tratados hipocráticos según la cual cada órgano y estructura del cuerpo producía pequeños sedimentos llamados gémulas, que por vía sanguínea… …   Wikipedia Español

  • Pangenesis — Pan*gen e*sis, n. [Pan + genesis.] (Biol.) An hypothesis advanced by Darwin in explanation of heredity. [1913 Webster] Note: The theory rests on the assumption, that the whole organization, in the sense of every separate atom or unit, reproduces… …   The Collaborative International Dictionary of English

  • pangenesis — pangenesis. См. пангенез. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Pangeněsis — (griech.), s. Erblichkeit, S. 892 …   Meyers Großes Konversations-Lexikon

  • Pangenesis — Pangenĕsis (grch.), nach Darwin die Annahme, daß sich die Zellen des tierischen Organismus nicht nur durch Teilung fortpflanzen, sondern auch kleinste, molekülartige Körnchen (Keimchen, gemmŭlae) abgeben, die sich nach Durchwanderung des Körpers… …   Kleines Konversations-Lexikon

  • pangénesis — Teoría darwiniana de que cada célula y partícula de un progenitor se reproduce a sí misma en la descendencia. Diccionario Mosby Medicina, Enfermería y Ciencias de la Salud, Ediciones Hancourt, S.A. 1999 …   Diccionario médico

  • pangenesis — [pan jen′ə sis] n. [ModL: see PAN & GENESIS] a former hypothesis of heredity in which each unit or cell of the body throws off very minute particles (pangenes) into the blood which circulate freely, undergo division, and are collected in the… …   English World dictionary

  • Pangenesis — Francis Galton, ein Vetter von Charles Darwin, zweifelte als einer der ersten die Pangenesistheorie an Pangenesis ist ein Begriff aus der Genetik und war methodischer Ansatz Charles Darwins bei seiner Arbeit Die Variation von Tieren und Pflanzen… …   Deutsch Wikipedia

  • pangénesis — ► sustantivo femenino BIOLOGÍA Teoría que proponía que cada parte del cuerpo estaba representada por una partícula que se encontraba en la sangre. IRREG. plural pangénesis …   Enciclopedia Universal

  • pangenesis — noun Etymology: New Latin Date: 1868 a disproven hypothetical mechanism of heredity in which the cells throw off particles that collect in the reproductive products or in buds so that the egg or bud contains particles from all parts of the parent …   New Collegiate Dictionary