Monday, February 20, 2006


[evomech] Research points to new theory driving evolutionary changes ('04 PR + Article)


1) Research points to new theory driving evolutionary changes (Press Release)

DALLAS - Dec. 13, 2004 - Researchers at UT Southwestern Medical Center at Dallas have used canine DNA to identify a genetic mutation mechanism they believe is responsible for rapid evolutionary changes in the physical appearance of many species.

The findings, based on data gathered from hundreds of museum specimens of dogs and from blood samples of volunteered live dogs, offer a new explanation for the sudden, rapid rise of new species found in the fossil record. They also help explain the variability in appearance among individual members of a species, such as the length of the nose in different breeds of domestic dogs.

"We're offering an explanation for a lot of different components of evolution, one that goes against the central dogma that currently explains how certain aspects of evolution take place," said Dr. Harold "Skip" Garner.

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2) Molecular origins of rapid and continuous morphological evolution

[Garner & Fondon, PNAS, Dec '04]


Mutations in cis-regulatory sequences have been implicated asbeing the predominant source of variation in morphologicalevolution. We offer a hypothesis that gene-associated tandem repeat expansions and contractions are a major source of phenotypic variation in evolution. Here, we describe a comparative genomic study of repetitive elements in developmental genes of 92 breeds of dogs. We find evidence for selection for divergence at coding repeat loci in the form of both elevated purity and extensive length polymorphism among different breeds. Variations in the number of repeats in the coding regions of the Alx-4 (aristaless-like4) and Runx-2 (runt-related transcription factor 2) genes were quantitatively associated with significant differences in limb and skull morphology. We identified similar repeat length variation in the coding repeats ofRunx-2, Twist, and Dlx-2 in several other species. The high frequency and incremental effects of repeat length mutations provide molecular explanations for swift, yet topologically conservative morphological evolution.

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John Latter

Model of an Internal Evolutionary Mechanism

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