Paralogue

Part of speech: noun

Definitions

1. A gene copy within a single genome that arose from duplication of an ancestral gene ; an optional side mission or chapter in certain role-playing games such as Fire Emblem
2. A duplicated gene found within the same genome as its evolutionary relative ; a voluntary side story chapter featured in some strategy and role-playing video games
3. Genes in one genome that diverged through internal duplication ; optional side missions offered in certain tactical video games, notably the Fire Emblem series

Etymology: "Paralogue" is a compound built from two Greek elements, "para" meaning "beside" or "alongside," and "logos," which gave English the "-logue" ending through words like "dialogue" and "monologue." The result was a word for something that runs alongside the main text or story rather than within it. That sense is exactly what makes the word useful in biology. A paralogue is a gene that sits alongside another copy of itself inside the same genome. When a gene was duplicated, the two copies could drift apart over time and take on different jobs, while the original text of the genome stayed intact. Biologists needed a term for these side-by-side copies, distinct from orthologues, which are matching genes in different species. Role-playing games borrowed the idea for their own side content. A paralogue in a game like Fire Emblem is an optional mission or chapter that runs beside the main story line, so players can detour into it without changing the central plot.