In Biology of the evolution, a homology indicates a similarity between two milked (in general, Anatomique S) observed at two Espèce S different, which is due to the fact that both inherited it a common ancestor. These features are then known as homologous . It can be anatomical, or molecular characters (Protéine S counterparts). This term also extends to the genetic sequences (of the DNA).
It is the case, for example, of the forefoot of a Cheval and pectoral Nageoire of a dolphin, just like these two animals, their ancestor common was a Mammifère (which, it there has 80 million years, probably resembled a Chevrotain), it thus had four members and it is the forelimb of this primitive mammal which gave the leg of the horse and the fin of the dolphin.
When two features appear independently in two tax without being the heritage of a common ancestor like the Ailes of the insects and those of the Oiseaux, one speaks about analogy .
Molecular levelHomologous proteins are proteins whose genes which code them have a common origin. 2 homologous proteins are recognized because they have close space structures and sequences in Amino-acid which present similarities. The functions of these proteins can be more or less similar.
One can find proteins homologous in different Espèce S, it is the case of the Globine S of the Vertébré S. That translated the common origin several species and thus the evolution. One can find proteins homologous in the same species, in fact the case of the globines alpha and beta compose the human Hémoglobine. That shows that the evolution can be due to a complexification of the Génome S.
Genetic homologyAugust 1st
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