Context crucial when it comes to mutations in genetic evolution, study reports

June 13, 2013

With mutations, it turns out that context can be everything in determining whether or not they are beneficial to their evolutionary fate.

According to the traditional view among biologists, a central tenet of has been that the evolutionary fates of new mutations depend on whether their effects are good, bad or inconsequential with respect to reproductive success. Central to this view is that "good" mutations are always good and lead to reproductive success, while "bad" mutations are always bad and will be quickly weeded out of the gene pool.

However, new research led by Jay Storz of the University of Nebraska-Lincoln has found that whether a given mutation is good or bad is often determined by other mutations associated with it. In other words, is context-dependent.

In a study to be published in the June 14 issue of Science, Storz and colleagues at UNL and Aarhus University in Denmark report that an individual mutation can be beneficial if it occurs in combination with certain other mutations, but the same mutation can detrimental to the organism if it occurs in other combinations.

The researchers studied mutations that alter the function of hemoglobin, the protein in charge of transporting oxygen in the blood. Physiologists have long known that many high-altitude animals have evolved hemoglobins with high affinities for oxygen, which can enhance in thin air. Earlier research by Storz's group on populations of North American deer mice that are native to high and low altitudes had found that the high-altitude mice had evolved hemoglobins with an increased oxygen-—and that this difference is attributable to the combined effects of at 12 different sites in the .

For the discovery reported in Science, the researchers used a technique called "" to synthesize hemoglobin proteins that contained each of the naturally occurring mutations in all possible multi-site combinations.

"By measuring the oxygen-binding properties of these engineered hemoglobins, we discovered that the same individual mutations produced an increased oxygen-affinity in some combinations and they produced a decreased oxygen-affinity in other combinations. Their effects are completely context-dependent," said Storz, an associate professor of biological sciences.

"One of the important implications is that if there are interactions between mutations, then some mutational pathways of evolution may be more accessible than others. The evolutionary fate of a new mutation will depend critically on which other mutations have already occurred. The order in which mutations occur can determine whether evolution is more likely to follow some pathways rather than others. Evolution may follow certain pathways just because certain interactions may be negative, other interactions may be positive. These kinds of interaction effects determine what mutational pathways are open and available for evolution."

Explore further: Biologists identify the molecular basis of high-altitude adaptation in mice

More information: "Epistasis Among Adaptive Mutations in Deer Mouse Hemoglobin," by C. Natarajan et al. Science, 2013.

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evolution3
3 / 5 (1) Jun 14, 2013
That's not correct. How is that something "new"? Nobody recently thought, that mutations are always good, bad or neutral? What is a resistance against some drug good for, if that drug doesn't exist? What would an oxygen binding molecule be good for, if there was almost no oxygen around as in before the great oxidation event 2,4 bio years ago? OF COURSE weather something is beneficial or not is context dependant. There is something called natural selection. And what is selected for is dependant on the system that organism lives in.
The same goes for mutations. A mutation that occurs in one specific genepool might be beneficial in that, but detrimental in another as some mutations interfer with each other and some might work together.
Come on, how is that big news?

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