Biology

The origins and evolution of de novo genes
Corbin Jones, University of North Carolina at Chapel Hill

“As natural selection acts solely by accumulating slight, successive, favourable variations, it can produce no great or sudden modification; it can act only by very short and slow steps.” --Charles Darwin, The Origin of Species, 1859.

The conventional wisdom among biologists is that adaptations result from gradual modifications. Molecularly, gene function was thought to evolve via changes in expression and/or changes in gene sequences (e.g., changes in amino acid sequence for protein-coding genes). New genomic data, however, suggest that molecular evolution may be more saltational than previously thought. Indeed, recent evidence suggests that wholly novel genes—that is, new genes unrelated to any pre- existing genes—arise surprisingly often. Though these de novo genes are a minority of genes in a genome, they may be of particular importance for understanding the evolution of species-specific biological functions and adaptations. Our recent work on de novo genes in fruit flies (Drosophila) demonstrated their existence, described their genomic distribution, detailed their expression patterns, and proposed a mutational and evolutionary mechanism for their origin.

Remarkably, these genes appear to arise from stretches of DNA that occur between protein coding genes. These observations suggest that these stretches of “non-functional” DNA may be an important source of genetic innovation.

1. Begun, D.J., et al., Evidence for de novo evolution of testis- expressed genes in the Drosophila yakuba/Drosophila erecta clade. Genetics, 2007. 176(2): p. 1131-7.

2. Levine, M.T., et al., Novel genes derived from noncoding DNA in Drosophila melanogaster are frequently X-linked and exhibit testis- biased expression. Proc Natl Acad Sci U S A, 2006. 103(26): p. 9935-9.

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Biology

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