User:AsteforiiAlbicans/Introgression

Fragments
Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Purposeful introgression is a long-term process; it may take many hybrid generations before the backcrossing occurs.

Introgression differs from simple hybridization. Introgression results in a complex mixture of parental genes, while simple hybridization results in a more uniform mixture, which in the first generation will be an even mix of two parental species, such as is observed in mules. Introgression or introgressive hybridization is the incorporation (usually via hybridization and backcrossing) of alleles ( genes or gene variants ?) from one entity (species) into the gene pool of a second, divergent entity (species)   ( perhaps say "distinct taxon" or just "species". There shouldn't need to be clarification ). Ancient introgression events can leave traces of extinct species in present‐day genomes, a phenomenon known as ghost introgression.

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Lineage fusion is an extreme type of introgression