Biologists seeking elusive proof of natural selection at the single-gene level have a powerful new tool at their disposal. Chris Toomajian, postdoctoral researcher in molecular and computational biology in the USC College of Letters, Arts and Sciences, led a group that sought to replace the standard neutral model, a common but unrealistic test for natural selection, with a statistical method based on hard genomic data.
The group’s research will be published online April 25 by Public Library of Science. "Do we now have enough data to see the standard neutral model wasn’t appropriate?" Toomajian asked. "We know something more now about how the population has been structured."
The standard neutral model makes improbable assumptions about population structure, such as assigning each individual an equal chance of reproducing.
Co-author Magnus Nordborg, associate professor of molecular and computational biology in USC College, predicted that earlier research would need to be revisited because the model makes it too easy to infer selection at any given gene. "Once you start looking at enough cases then you realize that, oops, it’s all under selection. I think a lot of that research is going to end up in the trash can," Nordborg said.
The group’s method can be applied to any organism, including humans. The PLoS paper focused on the weed Arabidopsis thaliana, and in particular on the FRIGIDA (FRI) gene, known to influence flowering time. A. thaliana was once a plant that bloomed annually. But two versions of FRI that appeared thousands of years ago enabled the plant to flower year-round, helping it out-compete other plants.
Toomajian and his group showed that these two versions, also called gene variants, are too common to have spread solely by chance. "We’ve shown that for one gene with an important role in that [flowering] process, there’s good evidence that there’s natural selection changing the behavior of the plants," Toomajian said. Why the variants were selected remains unclear, though some have suggested that the plant evolved under pressure from the spread of agriculture. Toomajian’s group identified the gene variants through a comparison of 96 plants over 1,102 short fragments of the genome.
Each variant was assigned a score based on the similarity of two plants around the FRI gene relative to their similarity at other regions in the genome. The higher the score, the less likely it is that a variant could have arisen and spread randomly. The scoring formula accounts for the greater similarity expected in related plants.
Nordborg said that while natural selection is well documented at the whole-organism level, researchers consider biochemical proof of selection "the Holy Grail" of population genetics. "What has proven very difficult is to connect specific molecular changes to selection," Nordborg said. The PLoS paper, along with other recent studies based on intrinsic genomic comparisons, brings biology closer to this goal.
Carl Marziali | EurekAlert!
CWRU researchers find a chemical solution to shrink digital data storage
22.06.2017 | Case Western Reserve University
Warming temperatures threaten sea turtles
22.06.2017 | Swansea University
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.
New Manufacturing Technologies for New Products
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
22.06.2017 | Medical Engineering
22.06.2017 | Life Sciences
22.06.2017 | Life Sciences