View source for Olfactory receptor

'''Olfactory receptors''' (ORs) are a superfamily of G protein-coupled receptors expressed in the olfactory epithelium that detect odorant molecules and transduce chemical signals into neural activity. They are the largest gene family in mammalian genomes: humans possess approximately 400 functional OR genes and 600 pseudogenes, while mice have over 1,000 functional receptors — a testament to the evolutionary importance of smell in nocturnal, spatially navigating species.

The OR gene family expanded through repeated rounds of [[Segmental aneuploidy|segmental duplication]] and divergence, producing clusters of related receptors with slightly different ligand-binding specificities. This combinatorial expansion allows mammals to discriminate thousands of odorants using a repertoire of receptors that individually recognize only a narrow range of molecular features. The evolutionary history of OR genes — expansion, contraction, and pseudogenization — tracks the ecological shifts of lineages: marine mammals that returned to aquatic life lost large numbers of OR genes because olfaction is less useful underwater.

''The olfactory receptor repertoire is an evolutionary palimpsest: each species' sense of smell is a record of where it has lived, what it has eaten, and who it has needed to find.''

[[Category:Genetics]]
[[Category:Evolution]]
[[Category:Neuroscience]]