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The developmental genetics of homology

Nature Reviews Genetics volume 8, pages 473–479 (2007)Cite this article

Abstract

Homology is an essential idea of biology, referring to the historical continuity of characters, but it is also conceptually highly elusive. The main difficulty is the apparently loose relationship between morphological characters and their genetic basis. Here I propose that it is the historical continuity of gene regulatory networks rather than the expression of individual homologous genes that underlies the homology of morphological characters. These networks, here referred to as 'character identity networks', enable the execution of a character-specific developmental programme.

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Figure 1: Homology of morphological characters.
Figure 2: Homologous characters can have different shapes and functions.
Figure 3: Characters and character states.
Figure 4: Ubx determines character identity, not character states.
Figure 5: Gene regulatory networks for eye development.

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Acknowledgements

The author gratefully acknowledges the financial support for the research that led to the ideas expressed in this article: NSF IBN#0321470, OIB#0445971 and the Research Prize from the Alexander von Humboldt Foundation. I also want to thank the reviewers of this paper as well as M. Laubichler, M. Ghiselin, E. Wiley, M. Donaghue, A. Monteiro and the members of my laboratory for discussion and inspiration.

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  1. Günter P. Wagner is at the Department of Ecology and Evolutionary Biology, Yale University, POB 208106, New Haven, Connecticut 06520-8106, USA. gunter.wagner@yale.edu,

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Glossary

Orthologue

Two genes are orthologues if their lineages are connected through a speciation event and without a duplication event.

Paralogue

Two genes are paralogues if their lineages are connected through a gene duplication event.

Pro-orthologue

For example, when one species has two copies of a gene, say Ga and Gb, and another species has a single copy G, and the speciation event that separated the species lineages occurred earlier than the gene duplication event, G is the pro-orthologue of Ga and Gb.

Semi-orthologue

For example, if G is the pro-orthologue of Ga and Gb, then both Ga and Gb are the semi-orthologues of G.

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Wagner, G. The developmental genetics of homology. Nat Rev Genet 8, 473–479 (2007). https://doi.org/10.1038/nrg2099

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