paraloge

Paralogue (plural paralogues or paralogs) refers to a gene that is related to another gene in the same organism due to descent from a gene duplication event. Paralogs arise when a gene is duplicated within a genome, producing two or more copies that can accumulate mutations independently. Over time, paralogous genes may diverge in sequence and function, or one copy may become nonfunctional.

Origins and outcomes: paralogues originate through various duplication mechanisms, including unequal crossing over, replication errors, retrotransposition, or whole-genome duplications. After duplication, divergent evolution can lead to subfunctionalization, where each copy retains a subset of the ancestral function, or neofunctionalization, where one copy gains a new function. Some paralogues remain functionally redundant or are maintained due to dosage requirements. Others become pseudogenes if they accumulate disabling mutations.

Paralogues versus orthologues: paralogous genes are related by duplication within a species, while orthologous genes are related by speciation and are found in different species. Distinguishing paralogues from orthologues is important for inferring gene function and evolutionary relationships.

Examples: many gene families in humans and other vertebrates are paralogous, such as the beta-like and alpha-like globin gene clusters, which arose through duplications and diversified in function and expression patterns. The olfactory receptor gene family is another extensive set of paralogous genes generated by repeated duplications.

Pseudogenes: some paralogous copies become pseudogenes and lose coding potential, though they may influence regulation or regain function in rare cases.

Evolutionary significance: duplication-driven expansion of gene repertoires provides raw material for genetic innovation, enabling new biochemical activities, regulatory networks, and adaptability across lineages.