A hypothesis on the role of transposons.

Genomic transposable elements, or transposons, are sequences of DNA that can move to different positions in the genome; in the process, they can cause chromosomal rearrengements and changes in gene expression. Despite their prevalence in the genomes of many species, their function is largely unknown: for this reason, they have been labelled "junk" DNA. "Epigenetic Tracking" is a model of development that, combined with a standard evolutionary algorithm, become an evo-devo method able to generate arbitrary shapes of any kind and complexity (in terms of number of cells, number of colours, etc.). The model of development has been also shown to be able to produce the artificial version of key biological phenomena such as the phenomenon of ageing, and the process of carcinogenesis. In this paper the evo-devo core of the method is explored and the result is a novel hypothesis on the biological role of transposons, according to which transposition in somatic cells during development drives cellular differentiation and transposition in germ cells is an indispensable tool to boost evolution. Thus, transposable elements, far from being "junk", have one of the most important roles in multicellular biology. Copyright 2010 Elsevier Ireland Ltd. All rights reserved.