Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Research points to new theory driving evolutionary changes

14.12.2004


Researchers at UT Southwestern Medical Center at Dallas have used canine DNA to identify a genetic mutation mechanism they believe is responsible for rapid evolutionary changes in the physical appearance of many species.



The findings, based on data gathered from hundreds of museum specimens of dogs and from blood samples of volunteered live dogs, offer a new explanation for the sudden, rapid rise of new species found in the fossil record. They also help explain the variability in appearance among individual members of a species, such as the length of the nose in different breeds of domestic dogs.

The findings will appear in an upcoming issue of the Proceedings of the National Academy of Sciences and are available online. "We’re offering an explanation for a lot of different components of evolution, one that goes against the central dogma that currently explains how certain aspects of evolution take place," said Dr. Harold "Skip" Garner, professor of biochemistry and internal medicine at UT Southwestern and one of the authors of the study, which involved only small, non-invasive blood draws from dogs by licensed veterinarians.


The chemical units that make up an organism’s DNA, or genetic code, are abbreviated with the letters A, C, T and G. Strings of these letters spell out the genetic instructions needed to carry out all of life’s functions.

Most scientists agree that over very long periods of time, mutations in the genetic code are responsible for driving evolutionary changes in species. One widely accepted hypothesis is that random, so-called single-point mutations - a change from one letter to another among the billions of letters contained in the code - minutely but inexorably change an organism’s appearance.

UT Southwestern scientists, however, believe the single-point mutation process is much too slow and happens much too infrequently to account for the rapid rise of new species found in the fossil record, or for the rapid evolutionary changes occurring in species such as the domestic dog, whose various breeds have evolved relatively quickly from a not-too-distant common ancestor.

The scientists combined extensive genetic data from different dog breeds and data on the shapes of dog skulls with computer programs developed by study co-author Dr. John "Trey" Fondon, a research fellow in the Eugene McDermott Center for Human Growth and Development and biochemistry at UT Southwestern. The researchers found a correlation between the length and angle of the dogs’ noses and specific regions in their genetic code that are prone to mutate often.

These genetic regions, called tandem repeat sequences, consist of the same series of letters repeated many times over, for example, A-C-T-A-C-T-A-C-T. Mutations happen in these regions when such units - the A-C-T in the above example - are mistakenly added or subtracted by the proteins responsible for "reading" and "copying" the letters in the genetic instructions. Such additions or deletions can result in changes in the proteins made by cells, which then affects how the cells function and, over time, the physical appearance of an animal.

The researchers found that in a dog gene involved in determining muzzle length, the number of times specific tandem repeat units were repeated could be used as a predictor of what the dog looked like - long muzzle or short. In the same genetic region from wild coyotes and wolves, the researchers also found variations in repeat lengths, but these animals do not have nearly the wide range of variation in repeat length that domestic dogs do. Consequently, they also don’t have the range in physical variation in muzzle length.

Mutations in tandem repeat sequences occur much more frequently than single point mutations - up to 100,000 times as often - and are much more likely to result in significant morphological changes, or changes in physical appearance, in an organism, said Dr. Fondon, an evolutionary biologist.

"I was struck by the prevalence of very highly mutable tandem repeats in the coding regions of genes responsible for development," he said. "That’s when it occurred to me that this may be an important mechanism whereby our genomes are able to create lots of useful variations in genes that are important for our development, our shape and structure, and our overall appearance. "Many of the shape difference that we see in evolution are not suddenly adding a wing or a leg. They are distortions, the stretching or squishing of a body part. Mutations in these repeat sequences are responsible for such incremental, quantitative changes."

The researchers say the same processes may play an important role in the subtle variations between people. In addition, in humans and in other animals, tandem repeat sequences are found in genes responsible for neurological development, an area where humans have evolved rapidly.

"We have demonstrated that the tandem repeat sequences found in many genes are probably responsible for rapidly evolving physical traits that affect a species’ ability to survive," Dr. Garner said. "Dogs have been rapidly bred to have many different shapes and traits that are pleasing to humans, enabling them to survive. Humans rapidly evolved big brains, which helped them survive as well."

The next step in the research is to determine whether tandem repeat mutations behave in a similar manner in other animals, such as mice, and whether such genetic information can be used to predict what an animal will look like.

The research was funded by the National Cancer Institute and the Evelyn Hudson Foundation.

Amanda Siegfried | EurekAlert!
Further information:
http://www.utsouthwestern.edu

More articles from Life Sciences:

nachricht The interactome of infected neural cells reveals new therapeutic targets for Zika
23.01.2017 | D'Or Institute for Research and Education

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

Quantum optical sensor for the first time tested in space – with a laser system from Berlin

23.01.2017 | Physics and Astronomy

The interactome of infected neural cells reveals new therapeutic targets for Zika

23.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>