IMGT®, the international ImMunoGeneTics information system®

logo IMGT


An orphon is a gene identified in a chromosomal location outside the main loci.

An orphon is either pseudogene or ORF. It is not functional.
By extension, an orphon is an instance of the 'gene' concept of IMGT-ONTOLOGY [3].

Orphons belonging to a same group and localized on a same chromosome constitute a 'chromosomal orphon set'.

The term orphon was introduced by Childs et al. [4] to refer to "genetic elements that have lost their families". It was first applied to solitary members of histone and ribosomal gene families PMID: 6784929.

[1] Lefranc, M.-P. and Lefranc, G., The Immunoglobulin FactsBook, Academic Press, 458 pages (2001) ISBN: 012441351X
[2] Lefranc, M.-P. and Lefranc, G., The T cell receptor FactsBook, Academic Press, 398 pages (2001) ISBN: 0124413528.
[3] Giudicelli, V. and Lefranc, M.-P., Bioinformatics, 15, 1047-1054 (1999) PMID: 10745995, LIGM:221 pdf
[4] Childs, G. et al., Cell, 23, 651-663 (1981) PMID: 6784929