homologen

Homologs (or homologues) are entities that share a common ancestry. In biology, the term is used for chromosomes, genes, or proteins that descend from a single ancestral figure and retain a recognizable similarity in sequence or structure, even when their roles have diverged.

Homologous chromosomes are paired chromosomes in diploid organisms that carry the same genes in the same order, though the two copies (alleles) may differ. During meiosis, homologous chromosomes pair and can exchange genetic material through recombination. Homeologs refer to homologous genes in allopolyploid species derived from different parental genomes.

Homologous genes across species are related genes that diverged after a speciation event or gene duplication. Orthologs are homologous genes in different species that retain the same function, while paralogs arise by duplication within a species and may evolve new functions. Conserved synteny can provide clues to shared ancestry and help trace evolutionary relationships.

In chemistry, a homolog is a member of a homologous series—compounds that differ from adjacent members by a repeating unit, typically a CH2 group. The series shows gradual changes in properties such as boiling point and solubility; examples include the alkanes, alcohols, and carboxylic acids.