paralogos

Paralogos, commonly referred to as paralogs, are homologous genes within a single genome that arise by gene duplication. The duplicates may diverge in sequence and function over time, contributing to the expansion of gene families. Paralogs are distinguished from orthologs, which are homologous genes in different species derived from a common ancestral gene through speciation.

Duplication can occur via several mechanisms, including unequal crossing over, replication slippage, retroposition, or whole-genome duplication. After duplication, one copy may retain the original function while the other accumulates mutations, leading to subfunctionalization (partitioning of ancestral functions) or neofunctionalization (acquiring a new function). In some cases, duplicated genes become nonfunctional pseudogenes.

Paralogous genes play a central role in evolutionary innovation and phenotypic diversification, while also introducing redundancy and potential dosage constraints. Their retention and diversification are influenced by selective pressures and genomic context; some families remain highly conserved, whereas others rapidly expand. The arrangement of duplications—such as tandem arrays or segmental duplications—affects how paralogs evolve and are maintained in the genome.

Identification and study of paralogs rely on sequence similarity analyses, phylogenetic reconstruction, and synteny assessment. Notable paralogous families include the globin genes, Hox clusters, and many olfactory receptor genes in vertebrates, among others. Understanding paralogs sheds light on how gene duplication drives functional diversification and organismal complexity.