Friday, February 08, 2013

What is the meaning of Parthenogenesis? Concept, Definition of Parthenogenesis

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Definition of parthenogenesis


1 Meaning of parthenogenesis

Parthenogenesis is a form of reproduction based on the development of non-fertilized female sex cells, which occurs with some frequency in flatworms, rotifers, tardigrades, crustaceans, insects, amphibians and reptiles, more rarely in some fish and, exceptionally, in birds. Parthenogenesis was discovered by Charles Bonnet. Jan Dzierzon was the first to discover the parthenogenesis of the drone of bees.
It can be interpreted as asexual reproduction or sexual monogametica, since it involved a sex cell, gamete or egg.
It consists of the segmentation of the egg without fertilizing, put up by factors environmental, chemical, electric shock, etc. In some cases (fish), that refer to as geitonogamy, contact or with a male gamete fusion is required, but does not complete fertilization, not contributing the male cell with its genes.
The product, called partenote, can not carry specifically male chromosomes. According to the mode of sex determination, that may limit the descendants to only one of them, as in bees and other Hymenoptera insects, where females are diploid, from fertilized eggs, and Parthenogenetic, haploid males.
Although the procedure has tried also with male gametes, not has been still the development of embryos, because the male cells are usually reduced to the sole function of fertilizing, while the female ones are characteristically totipotent.


2. Definition of parthenogenesis

Parthenogenesis is a concept that is used in biology to name a reproductive mechanism that share certain animal and plant species. Parthenogenesis takes place when female sex cells repeatedly divide unless they have been linked previously to a type male gamete.
Due to its characteristics, parthenogenesis can be described as a sexual reproduction of monogametica type (because it has the intervention of a kind of sex cell) or, even, an asexual reproductive mechanism.
Various circumstances lead to that the egg segment until its fertilization occurs. It may be a chemical, environmental factor or another class that produces this reproduction. Scientists, on the other hand, have proven that there are certain bacteria that can change the genes of animals and cause parthenogenesis.
In the case of the plants, the apoximia is a reproductive mechanism that associates it with parthenogenesis, since it implies the generation of seeds without having fertilization or which meiosis occurs.
Parthenogenesis may qualify as ameiotica (when not develops meiosis, but mitosis, producing a diploid cell) or haploid (meiosis takes place and the cell that is created is of type haploid).
In the case of the mammalian parthenogenesis has been achieved (man-induced) in apes, mice and rabbits. They have also detected or achieved cases of parthenogenesis in other non-mammalian animals, as well as quail, turkeys, geckos, Dragons of Komodo, hammerhead sharks, bees and ants.

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