Orthology VS Paralogy

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Homologous sequences. Orthologs and Paralogs are two types of homologous sequences. Orthology describes genes in different species that derive from a common ancestor. Orthologous genes may or may not have the same function. Paralogy describes homologous genes within a single species that diverged by gene duplication.

Aussi :

Analogue:	An organ or structure that is similar in function to one in another kind of organism but is of dissimilar evolutionary origin (e.g. vertebrate and molluscan eyes).
Homologue:	Similar in structure and evolutionary origin, though not necessarily in function (e.g. the flippers of a seal and the hands of a human).
Orthologue:	Orthologues are genes in different species that evolved from a common ancestral gene by speciation. Normally, orthologues retain the same function in the course of evolution. Identification of orthologues is critical for reliable prediction of gene function in newly sequenced genomes.
Paralogue:	Paralogues are genes related by duplication within a genome. Orthologues retain the same function in the course of evolution, whereas paralogues evolve new functions, even if these are related to the original one.