title: Patterns of gene expression: homology or homocracy?
abstract: Numerous papers over the years have stated that the original meaning of the term homology is historical and morphological and denotes organs/structures in two or more species derived from the same structure in their latest common ancestor. However, several more recent papers have extended the use of the term to cover organs/structures which are organised through the expression of homologous genes. This usage has created an ambiguity about the meaning of the term, and we propose to remove this by proposing a new term, homocracy, for organs/structures which are organised through the expression of identical patterning genes. We want to emphasise that the terms homologous and homocratic are not mutually exclusive. Many homologous structures are in all probability homocratic, whereas only a small number of homocratic structures are homologous.
authors.affiliation: Zoological Museum, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark. cnielsen@zmuc.ku.dk
authors.forename: Claus
authors.initials: C
authors.lastname: Nielsen
authors.forename: Pedro
authors.initials: P
authors.lastname: Martinez
mesh_terms: D005075:Biological Evolution; D005136:Eye Proteins; D015870:Gene Expression; D005838:Genotype; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D010614:Pharynx / Q000254:growth & development; D010641:Phenotype; D012097:Repressor Proteins; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D014157:Transcription Factors; C117261:distal-less protein, insect