Monday, February 27, 2006
[evomech] Re: Symmetry Breaking and the Evolution of Development (Science)
--- In evomech@yahoogroups.com, "John Latter" <jorolat@...> wrote:
>
> [Palmer, Science, Oct '04]
>
> Abstract:
>
> " Because of its simplicity, the binary-switch nature of left-right asymmetry permits meaningful comparisons among many different organisms. Phylogenetic analyses of asymmetry variation, inheritance, and molecular mechanisms reveal unexpected insights into how development evolves. First, directional asymmetry, an evolutionary novelty, arose from nonheritable origins almost as often as from mutations, implying that genetic assimilation ("phenotype precedes genotype") is a common mode of evolution. Second, the molecular pathway directing hearts leftwardthe nodal cascadevaries considerably among vertebrates (homology of form does not require homology of development) and was possibly co-opted from a preexisting asymmetrical chordate organ system. Finally, declining frequencies of spontaneous asymmetry reversal throughout vertebrate evolution suggest that heart development has become more canalized."
>
> Copies of the full article can be obtained either by emailing Rich direct or from myself here
>
This paper is now available at:
http://www.biology.duke.edu/nijhout/PDFs/Palmer04.pdf
John Latter
Model of an Internal Evolutionary Mechanism
http://members.aol.com/jorolat/index.html
technorati tags: symmetry, evolution, inheritance, novelty, genetic+assimilation, phenotype, genotype, asymmetry, vetebrate
>
> [Palmer, Science, Oct '04]
>
> Abstract:
>
> " Because of its simplicity, the binary-switch nature of left-right asymmetry permits meaningful comparisons among many different organisms. Phylogenetic analyses of asymmetry variation, inheritance, and molecular mechanisms reveal unexpected insights into how development evolves. First, directional asymmetry, an evolutionary novelty, arose from nonheritable origins almost as often as from mutations, implying that genetic assimilation ("phenotype precedes genotype") is a common mode of evolution. Second, the molecular pathway directing hearts leftwardthe nodal cascadevaries considerably among vertebrates (homology of form does not require homology of development) and was possibly co-opted from a preexisting asymmetrical chordate organ system. Finally, declining frequencies of spontaneous asymmetry reversal throughout vertebrate evolution suggest that heart development has become more canalized."
>
> Copies of the full article can be obtained either by emailing Rich direct or from myself here
>
This paper is now available at:
http://www.biology.duke.edu/nijhout/PDFs/Palmer04.pdf
John Latter
Model of an Internal Evolutionary Mechanism
http://members.aol.com/jorolat/index.html
technorati tags: symmetry, evolution, inheritance, novelty, genetic+assimilation, phenotype, genotype, asymmetry, vetebrate
Please Note: If you are reading this in a Blog then replying directly to this message (as opposed to making a 'blog comment') requires membership of the 'Evolution: Where Darwin meets Lamarck?' Egroup at:
http://groups.yahoo.com/group/evomech/
Add to: CiteUlike | Connotea | Del.icio.us | Digg | Furl | Newsvine | Reddit | Yahoo
