Featured Research

from universities, journals, and other organizations

Most extensive pictures ever of an organism's DNA mutation processes

Date:
September 17, 2012
Source:
Indiana University
Summary:
Biologists and informaticists have produced one of the most extensive pictures ever of mutation processes in the DNA sequence of an organism, elucidating important new evolutionary information about the molecular nature of mutations and how fast those heritable changes occur.

This circle represents the Escherichia coli chromosome with 1,931 mutations. Blue lines represent base-pair substitutions and green lines represent the gain or loss of between one and four nucleotides.
Credit: Andrew J. Hanson, School of Informatics and Computing, Indiana University

Biologists and informaticists at Indiana University have produced one of the most extensive pictures ever of mutation processes in the DNA sequence of an organism, elucidating important new evolutionary information about the molecular nature of mutations and how fast those heritable changes occur.

Related Articles


By analyzing the exact genomic changes in the model prokaryote Escherichia coli that had undergone over 200,000 generations of growth in the absence of natural selective pressures, the team led by IU College of Arts and Sciences Department of Biology professor Patricia L. Foster found that spontaneous mutation rates in E. coli DNA were actually three times lower than previously thought.

The new research, which appeared September 17 in early edition of the journal Proceedings of the National Academy of Sciences, also notes that the mismatch repair proteins that survey newly replicated DNA and detect mistakes not only keep mutation rates low but may also maintain the balance of guanine-cytosine content to adenine-thymine content in the genome. Guanine-cytosine and adenine-thymine are the nitrogenous bases that bond between opposing DNA strands to form the rungs of the double helix ladder of DNA.

"We know that even in the absence of natural selection, evolution will proceed because new mutations get fixed at random in the genome," Foster said. "So, if we want to determine whether specific patterns of evolutionary change are driven by selection, knowledge of the expected pattern in the absence of selection is absolutely essential. Here we are defining the rate and molecular spectrum of spontaneous mutations while minimizing the ability of natural selection to promote or eradicate mutations, which allows us to capture essentially all mutations that do not cause the bacterium to die."

In a parallel mutation accumulation experiment using a strain defective in mismatch repair, in which the mutation rate was increased over 100-fold, the researchers analyzed nearly 2,000 mutations and found that these were strongly biased toward changing adenine-thymine base pairs to guanine-cytosine base pairs, the opposite of what is seen in the normal bacteria.

E. coli chromosome

"The molecular spectrum of spontaneous base-pair substitutions in almost all organisms is dominated by guanine-cytosine to adenine-thymine changes, which tends to drive genomes toward higher adenine-thymine content," Foster noted. "Because the guanine-cytosine content of genomes varies widely, there must be some selective pressure, or some non-adaptive mechanism, that can drive genomes back toward increased guanine-cytosine content."

The new research, co-authored by IU Bloomington School of Informatics and Computing associate professor Haixu Tang, Informatics predoctoral researcher Heewook Lee and Department of Biology postdoctoral researcher Ellen Popodi, demonstrates that mismatch repair is a major factor in the types of mutations that occur and in determining the base composition of the genome. Because the activity of mismatch repair can be influenced by the environment, another implication of this work is that the pattern of mutations could be used in forensics to help determine where a particular bacterial strain originated.

"By establishing baseline parameters for the molecular nature of spontaneous mutational change unbiased by selection, we can begin to achieve a deeper understanding of the factors that determine mutation rates, the mutational spectra, genomic base composition, how these may differ among organisms and how they may be shaped by environmental conditions," Foster said. "Since mutations are the source of variation upon which natural selection acts, understanding the rate at which mutations occur and the molecular nature of spontaneous mutational changes leads us to a fuller understanding of evolution."

The research took nearly two years to complete and was supported by a Multidisciplinary University Research Initiative Award from the U.S. Army Research Office.


Story Source:

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


Cite This Page:

Indiana University. "Most extensive pictures ever of an organism's DNA mutation processes." ScienceDaily. ScienceDaily, 17 September 2012. <www.sciencedaily.com/releases/2012/09/120917151721.htm>.
Indiana University. (2012, September 17). Most extensive pictures ever of an organism's DNA mutation processes. ScienceDaily. Retrieved April 19, 2015 from www.sciencedaily.com/releases/2012/09/120917151721.htm
Indiana University. "Most extensive pictures ever of an organism's DNA mutation processes." ScienceDaily. www.sciencedaily.com/releases/2012/09/120917151721.htm (accessed April 19, 2015).

Share This


More From ScienceDaily



More Health & Medicine News

Sunday, April 19, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Our Love Of Puppy Dog Eyes Explained By Science

Our Love Of Puppy Dog Eyes Explained By Science

Newsy (Apr. 17, 2015) Researchers found a spike in oxytocin occurs in both humans and dogs when they gaze into each other&apos;s eyes. Video provided by Newsy
Powered by NewsLook.com
Dr. Oz Under Fire For 'Quack Treatments' Yet Again

Dr. Oz Under Fire For 'Quack Treatments' Yet Again

Newsy (Apr. 17, 2015) Ten doctors signed a letter urging Columbia University to drop Dr. Oz as vice chair of its department of surgery, saying he plugs "quack" treatments. Video provided by Newsy
Powered by NewsLook.com
Scientists Find Link Between Gestational Diabetes And Autism

Scientists Find Link Between Gestational Diabetes And Autism

Newsy (Apr. 17, 2015) Researchers who analyzed data from over 300,000 kids and their mothers say they&apos;ve found a link between gestational diabetes and autism. Video provided by Newsy
Powered by NewsLook.com
Video Messages Help Reassure Dementia Patients

Video Messages Help Reassure Dementia Patients

AP (Apr. 17, 2015) Family members are prerecording messages as part of a unique pilot program at the Hebrew Home in New York. The videos are trying to help victims of Alzheimer&apos;s disease and other forms of dementia break through the morning fog of forgetfulness. (April 17) Video provided by AP
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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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