A Tool Kit
July 23rd, 2007 by 
Mike Gene
In his book Endless Forms Most Beautiful, Sean Carroll explains the role of tool kit genes in the development of organisms. Tool kit genes express products that in turn regulate whether or not other genes are turned on during embryological development. As such, most of them are transcription factors that bind to regulatory regions of a gene, regions Carroll refers to as switches. What thus determines whether or not a particular gene is expressed during development is the combination of activated and repressed switches as a consequence of the composition of the tool kit gene products available.
The teleological echo of all this can be seen from more than one angle.
For example, Carroll writes:
The distribution of the genes in the tool kit tells us that the tool kit is ancient and was in place prior to the evolution of most types of animals. (p. 79)
Such observations clearly fit into the hypothesis of front-loading I’ve been discussing for some time, something I hope to further explore for years to come. But there is also something more subtle.
For example, when talking about the development of the fly wing, Carroll notes:
The position of these veins and the spaces between the veins are marked out by the tool kit genes long before the veins actually form, about a week before the bug actually flies. (p. 97)
And the same theme is repeated when describing the development of the vertebrate brain:
Before these subdivisions are evident, and long before their functions are established and integrated, tool kit genes mark out the regions of the neural tube that are fated to become part of the brain. (p. 100)
Of course, this all makes sense as part of a developmental program. But what if we shift our focus just a bit and ask a simple question – are there tool kit genes for evolution itself? Evolution does not have to run as a tightly integrated program, mind you, but are there genes that mimic such developmental tool kit genes, by acting on genomes in ways that thus “mark out” trajectories that subsequent evolution can travel?
Posted in General | 
July 23rd, 2007 at 8:21 pm
[…] More These icons link to social bookmarking sites where readers can share and discover new web pages. […]
July 24th, 2007 at 12:56 pm
[…] Sean Carroll’s attempts to keep evo-devo Darwinian gets a look over. The distribution of the genes in the tool kit tells us that the tool kit is ancient and was in place prior to the evolution of most types of animals. (p. 79) […]
July 28th, 2007 at 6:12 pm
[…] After suggesting the existence of an evolution tool kit, how would one go about identifying the contents of such a tool kit? We would need to assign the functional role of ‘evolution’ to specific genes. Typically, biologists classify genes according to their functional roles. But they don’t assign evolution itself as a functional role. […]
September 24th, 2007 at 8:07 pm
[…] For years, I have been trying to flesh out the conceptualization of front-loading evolution at the origin of life. A working hypothesis has been that the first cells (uni-cellular life forms) were front-loaded with information that would facilitate the evolution of multi-cellular life. One possible candidate for such front-loaded ‘information’ would be the homeodomain proteins. These proteins play essential roles in metazoan development and are considered part of the developmental toolkit as outlined by biologist Sean Carroll. […]
October 20th, 2007 at 1:11 am
[…] For years, I have been trying to flesh out the conceptualization of front-loading evolution at the origin of life. A working hypothesis has been that the first cells (uni-cellular life forms) were front-loaded with information that would facilitate the evolution of multi-cellular life. One possible candidate for such front-loaded ‘information’ would be the homeodomain proteins. These proteins play essential roles in metazoan development and are considered part of the developmental toolkit as outlined by biologist Sean Carroll. […]