Friday, January 1, 2010

Plants to People: the Swift Tempo of Spontaneous Mutation

Research published today in the journal Science serves to further calibrate the ticking clock of genetic mutation. By tediously analyzing the genomes from multiple generations of the plant Arabidopsis thaliana, scientists from the Max Planck Institute have shown that spontaneous mutations can arise rather frequently in the genome. Despite commonly held assumptions of minimally effectual rarity, the study demonstrates that the rate at which novel mutations occur have more than ample potency to drive evolution. Moreover, when considering the total population size of Arabidopsis, the tempo of mutation indicates that evolution likely proceeds much faster than previously suspected.

Although a single seed of Arabidopsis thaliana may only posses a single point mutation (i.e. a single base or ‘letter’ of DNA) relative to its parents, when multiplied by millions of individual plants over multiple generations, that single mutation quickly compounds to produce tens of new base pairs in only a few years time. The rate of genetic change revealed by the Max Planck study not only aids our understanding of how observed resistance to chemical herbicides rapidly evolves within the weedy plants combated by agriculture, its findings also point to possibly underestimated speeds of mutation in other organisms – like those of humans.

For example, back in September a team headed by Sanger scientists published work in which the rate of mutation in humans was estimated at around 1 mutation per 15 to 30 million nucleotides. Comparatively, this estimate translates to about 150 point mutations in every individual as measured against their parents; that’s a mutation tempo 100 times fold that of Arabidopsis thaliana.

Ossowski, S., Schneeberger, K., Lucas-Lledo, J., Warthmann, N., Clark, R., Shaw, R., Weigel, D., & Lynch, M. (2009). The Rate and Molecular Spectrum of Spontaneous Mutations in Arabidopsis thaliana Science, 327 (5961), 92-94 DOI: 10.1126/science.1180677

Xue, Y., Wang, Q., Long, Q., Ng, B., Swerdlow, H., Burton, J., Skuce, C., Taylor, R., Abdellah, Z., & Zhao, Y. (2009). Human Y Chromosome Base-Substitution Mutation Rate Measured by Direct Sequencing in a Deep-Rooting Pedigree Current Biology, 19 (17), 1453-1457 DOI: 10.1016/j.cub.2009.07.032

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