Groups of genes that are closely related in their DNA sequences and encode for similar products, known as protein isoforms, are usually classified as members of the same gene family. Although all members of a given gene family do contain related nucleotide sequences, they may also encode proteins with different functions that are expressed in different moments of cell physiology or embryo development. Studies of homology (i.e., common characteristics shared by genes of different species) and of evolutionary conservation, indicate that genes of the same family apparently share a common ancestor, from which they evolved through gene divergence. Another characteristic of genes pertaining to the same family is that their functions are either similar or complementary to the functions of other members of the same family.

The present gene divergence probably resulted from the convergence of several factors, such as: genetic spontaneous mutations, polimorphism (i...