Evolution of new genes captured

(Phys.org)—Like job-seekers searching for a new position, living things sometimes have to pick up a new skill if they are going to succeed. Researchers from the University of California, Davis, and Uppsala University, Sweden, have shown for the first time how living organisms do this.

The observation, published Oct. 19 in the journal Science, closes an important gap in the .

Scientists have long wondered how living things evolve new functions from a limited set of . 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 for positive selection?

Experiments in Roth's laboratory and elsewhere led to a model for the origin of a by a process of "innovation, 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 or boom in the IT sector might lead her to hone her and look for an IT position.

The most common way to increase 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, Liu 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.

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Journal information: Science

Provided by UC Davis
Citation: Evolution of new genes captured (2012, October 22) retrieved 15 September 2019 from https://phys.org/news/2012-10-evolution-genes-captured.html
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Oct 23, 2012
Ha! Direct observation of a process that, according to creationists, shouldn't exist.(it compromises the very tenet of creationism, ie no change) In a creationist world, all living things are exactly the way they were as when they were 'designed' and 'created' about 6500years ago. It can't be any other way, because mutation=change=evolution. And we all know about the incompatibility of THOSE two theories:) It doesn't matter that the process was 'forced' in a lab. Fact is, that it shouldn't exist/be possible at all, if the intent of the 'creator' was to be preserved...(or else 'creating', esp in the biblical manner would be a moot point and completely superfluous) And considering that all genuinely scientific theory/research AND evidence regarding our origins is worthless without the theory of evolution to hold it together and substantiate it, I am truly intrigued to see how the creationists are going to wriggle their way out of this one! Best Regards, DH66

Oct 23, 2012
Hold on there buddy...

Lucifer is changing those Genes to confuse his flock and keep them from God.

Further, you have no proof that Gene changes cause evolution.

As a good Conservative, I deny your foolish Objective Reality and substitute my own ideologically based reality.

Oct 23, 2012
Evolutionists are just in it for the money, the chicks, and the rubber.

Filthy anti-godites.

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