homòloga

Homòloga is the Catalan term for homolog, used in biology to describe genes, chromosomes, or anatomical structures that share a common ancestry. Elements classed as homologous originate from a single ancestral element and are inherited through descent.

In diploid organisms, homologous chromosomes are chromosome pairs that carry the same genes at the same loci, one inherited from each parent. During meiosis, recombination between homologs can occur, contributing to genetic diversity.

Genetic homologs are related by descent. Across species, such relationships are described as orthology (genes in different species that arose from a single ancestor by speciation) and paralogy (genes related by duplication within a genome). The term homology emphasizes shared ancestry rather than current function.

Homologous structures, or morphologies, are body parts that resemble one another because of common origin, even if they serve different roles. The classical example is the vertebrate forelimb: the human arm, cat leg, whale flipper, and bat wing share a basic bone plan.

In molecular biology, deep homology is observed in conserved sequences, such as HOX genes, that are maintained across distant groups.

It is important to distinguish homology from analogy, where similarities result from convergent evolution rather than shared ancestry. The study of homology underpins comparative anatomy, phylogenetics, and genomics.