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.

Related Articles


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 December 20, 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 December 20, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Saturday, December 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) — In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Reuters - Light News Video Online (Dec. 19, 2014) — Millions of monarch butterflies begin to descend onto Mexico as part of their annual migration south. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
The Best Protein-Filled Foods to Energize You for the New Year

The Best Protein-Filled Foods to Energize You for the New Year

Buzz60 (Dec. 19, 2014) — The new year is coming and nothing will energize you more for 2015 than protein-filled foods. Fitness and nutrition expert John Basedow (@JohnBasedow) gives his favorite high protein foods that will help you build muscle, lose fat and have endless energy. Video provided by Buzz60
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) — A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. 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:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

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