Journal Article

Signatures of adaptive evolution within human non-coding sequence

Chris P. Ponting and Gerton Lunter

in Human Molecular Genetics

Volume 15, issue suppl_2, pages R170-R175
Published in print October 2006 | ISSN: 0964-6906
Published online October 2006 | e-ISSN: 1460-2083 | DOI:
Signatures of adaptive evolution within human non-coding sequence

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The human genome is often portrayed as consisting of three sequence types, each distinguished by their mode of evolution. Purifying selection is estimated to act on 2.5–5.0% of the genome, whereas virtually all remaining sequence is considered to have evolved neutrally and to be devoid of functionality. The third mode of evolution, positive selection of advantageous changes, is considered rare. Such instances have been inferred only for a handful of sites, and these lie almost exclusively within protein-coding genes. Nevertheless, the majority of positively selected sequence is expected to lie within the wealth of functional ‘dark matter’ present outside of the coding sequence. Here, we review the evolutionary evidence for the majority of human-conserved DNA lying outside of the protein-coding sequence. We argue that within this non-coding fraction lies at least 1 Mb of functional sequence that has accumulated many beneficial nucleotide replacements. Illuminating the functions of this adaptive dark matter will lead to a better understanding of the sequence changes that have shaped the innovative biology of our species.

Journal Article.  3683 words.  Illustrated.

Subjects: Genetics and Genomics

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