Abstract
While much excitement has attended the discovery and study of circular RNAs, a new study in Cell Reports suggests that most mammalian circRNAs are not only functionless, but in fact costly. Comparison across three species is also consistent with the influential but rarely tested Drift-Barrier Hypothesis of molecular complexity. According to this hypothesis, nonessential genomic elements are slightly deleterious elements that fix by genetic drift and, thus, are generally more abundant in species with small effective population sizes. I discuss the implications of these new results for the Drift-Barrier hypothesis. In particular, I note the distinction between two classes of genomic elements, based on whether they are created by ‘standard’ small-scale mutations (basepair substitutions, indels, etc.) or larger, more idiosyncratic mutations (segmental duplications, transposable element propagation, etc.) I suggest that the Drift-Barrier Hypothesis is likely to apply to the former class, but perhaps not the latter class.
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This work was supported by National Science Foundation award number 1751372.
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Handling editor: David Liberles.
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Roy, S.W. Costly circRNAs, Effective Population Size, and the Origins of Molecular Complexity. J Mol Evol 89, 598–600 (2021). https://doi.org/10.1007/s00239-021-10033-1
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DOI: https://doi.org/10.1007/s00239-021-10033-1