Featured Research

from universities, journals, and other organizations

Non-independent mutations present new path to evolutionary success

Date:
June 3, 2011
Source:
Indiana University
Summary:
Mutations of DNA that lead to one base being replaced by another don't have to happen as single, independent events in humans and other eukaryotes, a group of biologists has learned after surveying several creatures' genomes.

Mutations of DNA that lead to one base being replaced by another don't have to happen as single, independent events in humans and other eukaryotes, a group of Indiana University Bloomington biologists has learned after surveying several creatures' genomes.

And, the scientists argue, if "point mutations" can happen in twos, threes -- even nines -- large evolutionary jumps are possible, especially when problems caused by a single point mutation are immediately compensated for by a second or third. The work appears in the latest issue of Current Biology.

"A similar phenomenon had been observed in bacteria," said Matthew Hahn, the project's principal investigator. "And the idea that this might be happening in eukaryotes has been around for a while. We are the first ones to use exhaustive genomic studies to show it's actually happening, and happening in a big way."

Hahn and two members of his lab, Ph.D. student Daniel Schrider and undergraduate Jonathan Hourmozdi, surveyed the disparate genomes of yeast (Saccharomyces cerevisiae), roundworm (Caenorhabditis elegans), fruit fly (Drosophila melanogaster), the model plant Arabidopsis thaliania and humans, and found that across the board, about three percent of new mutations are "multi-nucleotide mutations," or MNMs, perhaps the result of a single, error-prone DNA polymerase making two or more mistakes as it made its way down the chromosome. The group also studied human trios of parent-parent-offspring DNA, as well as the complete genomes of a Yan Chinese (YH01) and J. Craig Venter, cofounder of (and donor to) the Human Genome Project. The researchers found tens of thousands of likely MNMs.

MNMs were essentially defined by the proximity of two or more point mutations. Since mutations are rare, the statistical likelihood of finding two mutations within 20 or 100 bases of each other after a few generations (or a few replication events in the germ line) is low enough to assume two nearby mutations have a near-100 percent likelihood of being caused by the same mutational event.

Three percent of new mutations may not sound like a lot, but even rare genetic phenomena can be very powerful if they impact a creature's fitness, the measure of an individual's ability to survive and reproduce.

"There are cases where an organism could improve its fitness if it acquired multiple mutations that would each reduce fitness if they occurred individually," Schrider said. "In cases like this, the organism would not be able to reach the improved fitness state, as the less-fit intermediate states would be eliminated by natural selection. Cases like this are referred to as 'fitness valleys.'"

The exchange of a single base within a gene can have drastic consequences for the behavior of the protein that gene encodes. Sickle cell anemia, for example, which causes red blood cells to become rigid, sharp-edged, and resistant to oxygen absorption -- and is the cause of listlessness and excruciating pain in the humans who have it -- is caused by a point mutation.

The idea, Hahn and Schrider say, is that whatever problems a point mutation causes could be ameliorated by a second, with one point mutation compensating for the other in between generations. The scientists admit they expect this would be a very rare event. But possible.

"The most exciting implication of our work is that it raises the possibility that organisms could leap across fitness valleys and reach a higher-fitness state by acquiring multiple mutations simultaneously," Schrider said.

Hahn says he does not yet know of examples of genes in which valley leaping might have occurred, but that he and other researchers are eager to investigate.

"Our work provides evidence for a possible new mechanism of adaptation," Hahn said. "It also raises questions about whether thousands of supposedly independent mutations others have observed in important genes are truly independent. Some of these genes will need to be reanalyzed, because the recognition that some of these mutations are actually MNMs could have an impact on many analyses of DNA sequences."

But first, Hahn's group will try to see whether the MNMs they've found in humans conform to the mechanism geneticists have observed in humans' faultier DNA polymerases.

"It's satisfying to be able to be able to show that this is real," Hahn said. "I talked about this at a recent conference, and no matter who we talked to, they said the same sorts of things: 'Oh yeah I've seen those before, but I just thought it was a statistical anomaly.' People have seen the phenomenon but they just didn't know it was meaningful. We hope this gets people excited to go back and look at their old sequence data."

This work was supported by grants from the Sloan Foundation, the National Science Foundation, and the Indiana University Cox Scholarship Program.


Story Source:

The above story is based on materials provided by Indiana University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Daniel R. Schrider, Jonathan N. Hourmozdi, Matthew W. Hahn. Pervasive Multinucleotide Mutational Events in Eukaryotes. Current Biology, June 2, 2011 DOI: 10.1016/j.cub.2011.05.013

Cite This Page:

Indiana University. "Non-independent mutations present new path to evolutionary success." ScienceDaily. ScienceDaily, 3 June 2011. <www.sciencedaily.com/releases/2011/06/110602122254.htm>.
Indiana University. (2011, June 3). Non-independent mutations present new path to evolutionary success. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2011/06/110602122254.htm
Indiana University. "Non-independent mutations present new path to evolutionary success." ScienceDaily. www.sciencedaily.com/releases/2011/06/110602122254.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Newsy (July 27, 2014) The satellite is back under ground control after a tense few days, but with a gecko sex experiment on board, the media just couldn't help themselves. Video provided by Newsy
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins