Paralogous

Part of speech: adjective

Pronunciation: /pəˈræl.ə.ɡəs/

Definitions

1. Referring to genetic elements that have diverged from a shared ancestor through duplication and subsequently adopted different functions or characteristics
2. Describes genes or DNA segments that have originated by duplication within a genome and evolved new roles or features
3. Pertaining to genetic material that shares ancestry due to copying events, leading to variation in function

Etymology: Walter Fitch, an American molecular evolutionist, introduced the term "paralogue" in 1970 to distinguish two kinds of gene similarity. Genes that match because a species inherited them from a common ancestor through speciation were "orthologues," while genes that match because a duplication happened within one genome were "paralogues." The new name combined the Greek "para," meaning "beside" or "alongside," with the "-logue" ending from "homologue," which in turn comes from Greek "homologos," meaning "agreeing" or "corresponding in proportion." The Greek adjective "paralogos" already existed in classical usage, where it meant "irregular," "unreasonable," or "contrary to reason." Biologists borrowed the sound and rebuilt the sense around copies that sit beside one another in a genome. The adjective "paralogous" then follows the ordinary English pattern of adding "-ous" to a noun, so it describes a gene pair or segment related by that duplication.