Comparative biology / evolutionary biology · BEGINNER LESSON
Homologue
A homologue is a gene, structure, or other biological entity that shares common ancestry with a corresponding one in another lineage. In these sources, homologs are defined by shared origin, not by needing to look or work the same.
What a homologue is
A homologue is something in biology that is traced to the same ancestral origin as a counterpart in another species or lineage. The sources use this term for genes, embryonic primordia, adult structures, and other developmental components. The key point is ancestry: two homologs can be clearly related even if their final forms are not similar and even if their functions differ.
[1] 5. From Genes To Embryos To... [2] Computational strategies for cross-species knowledge transfer and ... [3] Classifying Convergences in the Light of Horizontal Gene Transfer
How scientists recognize homology
Homology is often inferred by comparing position in an organism’s body plan, embryonic origin, and gene expression patterns. For example, the sources describe field homology in brain regions that begin as shared embryonic primordia, then develop into different layers, nuclei, or cell types in different species. Here, the shared developmental field is the evidence, not exact appearance. A developmental field is a group of developing cells that tends to produce the same kind of tissue fate in a fixed position within the whole organism.
[1] 5. From Genes To Embryos To... [3] Classifying Convergences in the Light of Horizontal Gene Transfer
Limits and common confusion
Similarity of shape or function is not required for homology, and it can mislead when unrelated traits evolve independently. That independent evolution is called homoplasy when similar traits arise without shared ancestry. The sources also separate homologs from orthologs, which are homologous genes split by speciation, and paralogs, which are homologous genes created by duplication within a lineage. Function can diverge after these events, so homology does not guarantee the same job in the body or cell.
[1] 5. From Genes To Embryos To... [2] Computational strategies for cross-species knowledge transfer and ... [3] Classifying Convergences in the Light of Horizontal Gene Transfer
SEE THE IDEA
How homology is judged across species
A biological feature is traced back to the same ancestral origin.
Embryonic position, gene expression, or body-plan location can support the match.
The descendants may look or work differently in each species.
Shared origin is accepted even when similarity is weak or absent.
Ancestry and developmental context support the homology claim; final form may diverge.
Homology is identified by shared origin and developmental evidence, while later differences are expected and do not cancel the relationship.
TRY IT YOURSELF
Test your understanding
Choose an answer, then check the explanation.
PUT IT TOGETHER
Match each concept to its meaning
Drag a label onto its description, or select a label and then select a description. This also works with a keyboard.
4 pairs to match
Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.