Featured Research

from universities, journals, and other organizations

If junk DNA is useful, why is it not shared more equally?

Date:
January 31, 2011
Source:
University of Veterinary Medicine -- Vienna
Summary:
Recently, it has become clear that "junk DNA" performs a wide range of tasks. But why do some organisms have so much of it and others so little? A particular puzzle is posed by introns, stretches of DNA that interrupt the sequence of genes. Researchers propose a mechanism to account for the range of intron numbers observed between different species.

DNA was originally thought to have a single function: to help cells make the proteins they need. Any DNA that is not immediately required to produce proteins was written off as "junk" and deemed unworthy of study. Recently, however, it has become clear that junk DNA performs a wide range of important tasks. As a result, attention is shifting to asking why some organisms have so much of it and other organisms so little. A particular puzzle is posed by so-called "introns," stretches of DNA that interrupt the sequence of genes. Ashley Farlow, Eshwar Meduri and Christian Schlötterer of the University of Veterinary Medicine, Vienna now propose a mechanism to account for the range of intron numbers observed between different species.

Their theory is published in the current issue of the journal Trends in Genetics.

The presence of introns in genes requires cells to process "messenger RNA" molecules before synthesizing proteins, a process that is costly and often error-prone. It was long believed that this was simply part of the price organisms paid for the flexibility to create new types of protein but recent work has made it clear that introns themselves have a number of important functions. And so attention is gradually shifting to asking why some organisms have so few introns and others so many.

It seems likely that new introns are added to DNA when double-stranded DNA breaks -- which may arise from a variety of mechanisms -- are not repaired "correctly" but the newly created ends are instead joined to other fragments of DNA. Farlow and colleagues at the Institute of Population Genetics of the University of Veterinary Medicine, Vienna reasoned that introns may be lost by a similar mechanism. An examination of areas of DNA where introns are known to have been lost in organisms such as worms and flies provides support for their idea.

DNA breaks may be treated in one of two ways: correct repair (by a relatively time-consuming process known as "homologous recombination") or the rapid and error-prone joining of non-homologous ends. The two pathways are essentially separate and can compete with each other for DNA breaks to work with. The scientists at the University of Veterinary Medicine, Vienna now suggest that species-specific differences in the relative activity of these two pathways might underlie the observed variation in intron number.

The theory represents a fundamental change in the way we think about the evolution of DNA. Evolution has seen periods of large scale intron loss alternating with periods of intron gain and this has been interpreted as the result of changing selection pressure. However, the rates at which single species have gained and lost introns throughout evolution have been found to vary in parallel, consistent with Farlow's notion that the two processes are related. The new theory provides an alternative interpretation: changes in the activities of the "homologous" and "non-homologous" pathways for repairing DNA breaks could cause introns to be lost faster than they are gained, or vice versa.

The idea is consistent with what we currently know about intron numbers, which range from a handful in some simple eukaryotes to more than 180,000 in the human genome. And as Farlow says, "Linking intron gain and loss to the repair of DNA breaks offers a neat explanation for how intron number can change over time. This theory may account for the huge diversity we seen in intron number between different species."


Story Source:

The above story is based on materials provided by University of Veterinary Medicine -- Vienna. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ashley Farlow, Eshwar Meduri, Christian Schlötterer. DNA double-strand break repair and the evolution of intron density. Trends in Genetics, 2011; 27 (1): 1 DOI: 10.1016/j.tig.2010.10.004

Cite This Page:

University of Veterinary Medicine -- Vienna. "If junk DNA is useful, why is it not shared more equally?." ScienceDaily. ScienceDaily, 31 January 2011. <www.sciencedaily.com/releases/2011/01/110131133137.htm>.
University of Veterinary Medicine -- Vienna. (2011, January 31). If junk DNA is useful, why is it not shared more equally?. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2011/01/110131133137.htm
University of Veterinary Medicine -- Vienna. "If junk DNA is useful, why is it not shared more equally?." ScienceDaily. www.sciencedaily.com/releases/2011/01/110131133137.htm (accessed July 30, 2014).

Share This




More Plants & Animals News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Otters Enjoy Water Slides at Japan Zoo

Raw: Otters Enjoy Water Slides at Japan Zoo

AP (July 30, 2014) — River otters were hitting the water slides to beat the summer heatwave on Wednesday at Ichikawa City's Zoological and Botanical Garden. (July 30) Video provided by AP
Powered by NewsLook.com
In Virginia, the Rise of a New Space Coast

In Virginia, the Rise of a New Space Coast

AP (July 30, 2014) — Every summer, tourists make the pilgrimage to Chincoteague Island, Va. to see wild ponies cross the Assateague Channel. But, it's the rockets sending to supplies to the International Space Station that are making this a year-round destination. (July 30) Video provided by AP
Powered by NewsLook.com
Rodents Rampant in Gardens Around Louvre

Rodents Rampant in Gardens Around Louvre

AP (July 29, 2014) — Food scraps and other items left on the grounds by picnickers brings unwelcome visitors to the grounds of the world famous and popular Louvre Museum in Paris. (July 29) Video provided by AP
Powered by NewsLook.com
Jane Goodall Warns Great Apes Face Extinction

Jane Goodall Warns Great Apes Face Extinction

AFP (July 29, 2014) — The world's great apes face extinction within decades, renowned chimpanzee expert Jane Goodall warned Tuesday in a call to arms to ensure man's closest relatives are not wiped out. Duration: 00:58 Video provided by AFP
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