Paralogs

Part of speech: noun

Definitions

1. A type of gene that has evolved through duplication and diverged in function from its original parent gene
2. Genes that arise from duplication events and may play different roles or express varied characteristics over time
3. Duplication-derived genes that have acquired new functions, differing from their ancestral counterparts in specific biological contexts

Etymology: "Paralogs" is the plural of "paralog," a term from molecular biology for genes that arose when a gene was copied within the same genome and the two copies went on to diverge. The "para-" prefix comes from Greek and means "beside" or "alongside," while "-log" is a back-formation or clipped form tied to the Greek "logos" in the sense of a counterpart or corresponding item, so the word describes a gene sitting beside its own relative. The contrast with "orthologs" is what gives the term its usefulness. Orthologs are genes in different species that descend from a single gene in their last common ancestor, whereas paralogs trace back to a duplication event inside one lineage. Over time one copy may keep the original job while the other drifts, accumulates mutations, and takes on a new function in particular tissues or conditions.