homology, homologous (adj)

Richard Owen (1804-1892)

Term:homology, homologous(adj)

Origin: Anc Greek

όμοιος/homo(=same)

λόγος/logos(=word, speech, discourse, reason)

literally means  “agreeing”

Coined

In 1843, Richard Owen (1804-1892) defined homology as "the same organ in different animals under every variety of form and function" eg a bat's wing, a seal flipper, a cat's paw and a human hand nonetheless display a common plan of structure, with identical or very similar arrangements of bones and muscles. Owen stated that there must exist a common structural plan for all vertebrates, as well as for each class of vertebrates. He called this plan the archetype.

Definition

1) Similarity of nucleotide or amino acid sequence.

2) Homology describes organs or structures in different animals that have a common evolutionary origin.

3) Homologous chromosomes  concers chromosome of the same length and centromere position with genes for the same characteristics at corresponding loci.