Evo-devo gene toolkit

The evo-devo gene toolkit is the small subset of genes in an organism's genome whose products control the organism's embryonic development. Toolkit genes are central to the synthesis of molecular genetics, palaeontology, evolution and developmental biology in the science of evolutionary developmental biology (evo-devo).

Toolkit genes are highly conserved among phyla, meaning that they are ancient, dating back to the last common ancestor of bilaterian animals. For example, that ancestor had at least 7 Pax genes for transcription factors.

Differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. The majority of toolkit genes are components of signaling pathways, and encode for the production of transcription factors, cell adhesion proteins, cell surface receptor proteins (and signalling ligands that bind to them), and secreted morphogens, all of these participate in defining the fate of undifferentiated cells, generating spatial and temporal patterns, which in turn form the body plan of the organism. Among the most important of the toolkit genes are those of the Hox gene cluster, or complex. Hox genes, transcription factors containing the more broadly distributed homeobox protein-binding DNA motif, function in patterning the body axis. Thus, by combinatorial specifying the identity of particular body regions, Hox genes determine where limbs and other body segments will grow in a developing embryo or larva. A toolkit gene is Pax6/eyeless, which controls eye formation in all animals. It has been found to produce eyes in mice and Drosophila, even if mouse Pax6/eyeless was expressed in Drosophila.

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