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Does evolution in body patterning genes drive morphological change—or vice versa?
Author(s) -
Budd Graham E.
Publication year - 1999
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/(sici)1521-1878(199904)21:4<326::aid-bies9>3.0.co;2-0
Subject(s) - hox gene , homeotic gene , biology , evolutionary biology , hierarchy , population , genetics , gene , homeobox , adaptation (eye) , phenotype , gene expression , sociology , neuroscience , demography , economics , market economy
Increased understanding of the regulation of body patterning genes in development, especially the homeotic genes, has led to the revival of ideas suggesting that “saltational” modes of evolution are important. However, such models are problematic on the grounds of functional continuity and population genetics, and the more dramatic scenarios rely on an overinterpretation of the taxonomic hierarchy. This article proposes an alternative model for the evolution of Hox gene expression, stressing the need for incremental functional integration. One surprising implication of the model would be that mutations in Hox genes and their regulators have virtually no primary role in driving morphological evolution. Rather, morphological change through microevolutionary adaptation comes first, with Hox expression shifting only afterwards, presumably to make the building of the new body pattern more efficient or more stable. Such a model has affinities to Waddington's “genetic assimilation” but invokes discrete rather than continuous shifts in control of a particular morphology. BioEssays 21:326–332, 1999. © 1999 John Wiley & Sons, Inc.