Hybrid

See also: Hybrid (homonymy), Crossing

In Genetic, the hybridization (of the Greek hybris , illegitimate union), is the crossing of two individuals of two varieties, subspecies (intraspecific crossing), Espèce S (crossing interspecific) or kind S (intergeneric crossing) different. The hybrid presents a mixture of the characteristics Génétique S of the two parents. At the time of intraspecific crossings, the term Métis is also used.

Hybridization is however different from the genetic Engineering insofar as hybridization, even if it east can be caused by the man, can also occur naturally.

Hybridization and speciation

Hybridization is one of the bases of the Spéciation. Whereas the genetic mutation modifies one Gène, hybridization involves a combination of multiple changes which, if they are beneficial and stable, can in about fifty generations give birth to a new species. It is this phenomenon which lets think of the scientists who the life must be regarded as a genetic Continuum rather than like a whole of isolated species (See Théorie of the evolution).

Reproduction of the hybrids

Certain stable hybrids can reproduce by their seeds (Bos taurus/Bos indicus) but generally, they are sterile. At the plants, one can reproduce the hybrids by vegetative Multiplication (Bouturage or Greffage). Many sterile vegetable hybrids were made fertile by chemical treatment, change of temperature or irradiation.

Rétrocroisement

Rétrocroisement is used to transfer one or some desirable genes from a relative donor with a receiving relative in addition acceptable. He requires a repeated crossing of new hybrids to the recurring relative and the selection of desired gene of the relative donor.

Botanical

At the plants, one can create hybrids as a practitioner a Pollinisation controlled. The Czech Botanist Gregor Mendel then the American Luther Burbank or the Russian Agronome Ivan Mitchourine was precursors on the matter at the end of the XIXe century and at the beginning of the XXe century.

F1 hybrids

In English, Subsidiary First Generation: the hybrid seeds of F1 are the result of a crossing between two varieties or races of the same species, selected on several generations for certain characteristic features. To obtain F1 seeds, one must cross the original parents at each year. It is not advised to collect the seed S produced by the F1 hybrids because they will not accurately reproduce the features of their parents. It is said that these F2 seeds are unstable;

  • Aprium : hybrid of Plum tree (1/3) and of Apricot tree (2/3);
  • Caseille : hybrid of Cassissier and Currant bush thorny;
  • Limequat : hybrid of Kumquat and File ( Citrus aurantifolia × C. fortunella );
  • Pluot : hybrid of plum tree (2/3) and apricot tree (1/3).

The monohybrides are the Hybride S of the subsidiary generation 1 obtained starting from a bearing crossing on only one character, the such color of the flowers, the shape of seeds, etc

Technique of vegetable hybridization

Hybridization is obtained by manually withdrawing the Anthère S of the flowers of the relative female indicated in order to avoid a sometimes possible car-fecundation. Once the anthères " castrées" , one deposits ripe Pollen (taken on the selected male relative) on the Pistil of the female flower of the relative. The hybrid Seed which results door from it genetic information from the characters of the two parents.

If the hybrid obtained inherits desired qualities, one speaks then about effect Hétérosis or hybrid Vigueur.

A genetic system of Marqueur from now on is often used to cultivate on the long run only the most promising sowings. For example, to create new varieties of Apple S, one crosses two known varieties having interesting characteristics. The pips of the fruits obtained are sown but it is known that only 1/8 of sowings has the required Allèle S (color, conservation, sugar content, etc). To keep only these sowings, one carries out a genetic test on a ripe sheet as of the first year of sowing. If this one shows the presence of gene supporting a strong production of ethylene (which involves a bad conservation of the fruit), sowing immediately is eliminated. There exist also markers making it possible to know in advance the color of the future fruits. While thus proceeding, the hybrideurs concentrate their work only on sowings of value.

Monohybridism

The monohybridism is a type of crossing Génétique which makes it possible to follow the Hérédité of only one character.

The various forms of a character being generally controlled by different Allele S from same a Gene, one crosses individuals of pure Lignée such as for example of the individuals with yellow flowers with individuals with blue flowers and one observes the color of the flowers obtained. One will be able to thus define which is the allele Dominating and which is the Récessif.

When the crossing relates to two different characters, one speaks about dihybridism , and so on.

Zoology

See too

External bond

  • Hybrid F1 (theoretical explanation) on echange-tomates.net

  • selection of the plants
  • Hybridization of the Hybrid apple tree
  • in the Birds

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