Posts Tagged ‘evolution’
System-wide networks of proteins are indispensable for organisms. Function and evolution of these networks are among the most fascinating research questions in biology. Bioinformatician Thomas Rattei, University of Vienna, and physicist Hernan Makse, City University New York (CUNY), have reconstructed ancestral protein networks. The results are of high interest not only for evolutionary research but also for the interpretation of genome sequence data. Recently, the researchers published their paper in the renowned journal PLOS ONE.
Are you a monkey or a man? According to a recent study out of the University of Utah, that all depends on how hard you can punch. Compared with apes, humans have shorter palms and fingers and longer, stronger, flexible thumbs – features that have been long thought to have evolved so our ancestors had the manual dexterity to make and use tools.
“The role aggression has played in our evolution has not been adequately appreciated,” says University of Utah biology Professor David Carrier, senior author of the study, published recently in the Journal of Experimental Biology.
As our ancestors evolved, “an individual who could strike with a clenched fist could hit harder without injuring themselves, so they were better able to fight for mates and thus more likely to reproduce,” he says. Fights also were for food, water, land and shelter to support a family, and “over pride, reputation and for revenge,” he adds.
Evolution, often perceived as a series of random changes, might in fact be driven by a simple and repeated genetic solution to an environmental pressure that a broad range of species happen to share, according to new research.
Princeton University research published in the journal Science suggests that knowledge of a species’ genes — and how certain external conditions affect the proteins encoded by those genes — could be used to determine a predictable evolutionary pattern driven by outside factors. Scientists could then pinpoint how the diversity of adaptations seen in the natural world developed even in distantly related animals.
Scientists have long wondered how living things evolve new functions from a limited set of genes. One popular explanation is that genes duplicate by accident; the duplicate undergoes mutations and picks up a new function; and, if that new function is useful, the gene spreads.
“It’s an old idea and it’s clear that this happens,” said John Roth, a distinguished professor of microbiology at UC Davis and co-author of the paper.
The problem, Roth said, is that it has been hard to imagine how it occurs. Natural selection is relentlessly efficient in removing mutated genes: Genes that are not positively selected are quickly lost.
How then does a newly duplicated gene stick around long enough to pick up a useful new function that would be a target for positive selection?
Experiments in Roth’s laboratory and elsewhere led to a model for the origin of a novel gene by a process of “innovation, amplification and divergence.” This model has now been tested by Joakim Nasvall, Lei Sun and Dan Andersson at Uppsala.
In the new model, the original gene first gains a second, weak function alongside its main activity — just as an auto mechanic, for example, might develop a side interest in computers. If conditions change such that the side activity becomes important, then selection of this side activity favors increasing the expression of the old gene. In the case of the mechanic, a slump in the auto industry or boom in the IT sector might lead her to hone her computer skills and look for an IT position.
The most common way to increase gene expression is by duplicating the gene, perhaps multiple times. Natural selection then works on all copies of the gene. Under selection, the copies accumulate mutations and recombine. Some copies develop an enhanced side function. Other copies retain their original function.
Ultimately, the cell winds up with two distinct genes, one providing each activity — and a new genetic function is born.
Nasvall, Lei and Andersson tested this model using the bacterium Salmonella. The bacteria carried a gene involved in making the amino acid histidine that had a secondary, weak ability to contribute to the synthesis of another amino acid, tryptophan. In their study, they removed the main tryptophan-synthesis gene from the bacteria and watched what happened.
After growing the bacteria for 3,000 generations on a culture medium without tryptophan, they forced the bacteria to evolve a new mechanism for producing the amino acid. What emerged was a tryptophan-synthesizing activity provided by a duplicated copy of the original gene.
“The important improvement offered by our model is that the whole process occurs under constant selection — there’s no time off from selection during which the extra copy could be lost,” Roth said.
The work was supported by the Swedish Research Council and the National Institutes of Health.
Thank you to UCDavis for this story.