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Gene superfamily
A gene superfamily is one of the sub-categories under which a gene may be classified. Gene superfamilies are an order of classification less specific than that of a typical gene family. A gene superfamily is defined as a collection of genes that share a common origin. The product of the genes in a superfamily may or may not be similar in function.

A particular superfamily will only contain genes that have been determined to be similar in nature. Any genes containing domains that have a common origin will be members of a superfamily. Due to this fact, it is possible for a single gene to belong to multiple superfamilies. It is also possible for multiple members of a superfamily to exist within an individual organism.

Categorization of genes involves their phylogenetic origins. Genes that fit into a particular superfamily are found to have been evolutionarily derived from a particular ancestral gene or genetic sequence. As such, gene superfamilies consistently incorporate genes found within several distinct, though evolutionarily related species. Supplementary information for the classification of a gene into a superfamily can also include the biological function of the gene. The resultant protein or the final gene product of a gene may also come into consideration in grouping a gene into a particular superfamily.

The creation of a gene superfamily is commonly accredited to the duplication of a gene sequence by either tandem segmental duplication or retrotransposition. For the formation of a new gene superfamily to occur, an entire gene will normally undergo duplication. The duplication of a gene creates a new copy, which can be freely altered. These variations in the gene allow it to develop new functions or changes in efficiency of the gene product. The original copy remains intact and unchanged. The unchanged copy maintains normal function in the organism. This prevents the effects of the altered copy from potentially impeding the success of the organism. An important aspect of a gene superfamily is that there are differential expression patterns exhibited between the genes within that superfamily.

Notable gene superfamilies
Immunoglobulin superfamily

Olfactory receptor gene superfamily

P450 gene superfamily