Nav: Home

Scientists prove key aspect of evolutionary theory

January 26, 2016

Evolutionary theory predicts that pairs of chromosomes within asexual organisms will evolve independently of each other and become increasingly different over time in a phenomenon called the 'Meselson effect'.

While this event was first predicted almost twenty years ago, evidence for it has proved elusive.

Now, researchers from the University of Glasgow have demonstrated the Meselson effect for the first time in any organism at a genome-wide level, studying a parasite called Trypanosoma brucei gambiense (T.b. gambiense). Their findings are to be published in the journal eLife. The research was conducted at the Wellcome Trust Centre for Molecular Parasitology in the University's Institute of Biodiversity Animal Health and Comparative Medicine.

T.b. gambiense is responsible for causing African sleeping sickness in humans, leading to severe symptoms including fever, headaches, extreme fatigue, and aching muscles and joints, which do not occur until weeks or sometimes even months after infection.

These symptoms extend to neurologic problems, such as progressive confusion and personality changes, when the infection invades the central nervous system.

In order to demonstrate the Meselson effect in T.b. gambiense, the research team, led by Dr. Annette Macleod, sequenced the genomes of 85 isolates of the parasite, including multiple samples from disease focus points within Guinea, Cote d'Ivoire and Cameroon, collected over fifty years from 1952 to 2004.

The similarity of the genomes studied from these different locations, together with a lack of recombination in the evolution of the parasite, suggests that this sub-species emerged from a single individual within the last 10,000 years.

"It was around this time that livestock farming was developing in West Africa, allowing the parasite, which was originally an animal organism, to 'jump' from one species to the other via the Tsetse fly," says lead author Dr. Willie Weir.

"Since then, mutations have built up and the lack of sexual recombination in T.b. gambiense means that the two chromosomes in each pair have evolved independently of each other, demonstrating the Meselson effect."

Dr. Weir adds that the parasites' inability to recombine with each other prevents genes from being exchanged between strains. This could subsequently hamper the ability of the organism to develop resistance to multiple drugs.

The team also uncovered evidence that the parasite uses gene conversion to compensate for its lack of sex.

This mechanism essentially repairs the inferior, or mutated, copy of a gene on a chromosome by 'copying and pasting' the superior copy from the chromosome's partner. The future challenge will be to investigate the effectiveness of this mechanism in the long term, as evolutionary theory suggests that asexual organisms should eventually face extinction. If T.b. gambiense shares this fate, the major cause of African sleeping sickness will be eliminated - although it is impossible to predict when this might happen.
-end-
Reference

The paper 'Population genomics reveals the origin and asexual evolution of human infective trypanosomes' can be freely accessed online at http://dx.doi.org/10.7554/eLife.11473. Contents, including text, figures, and data, are free to reuse under a CC BY 4.0 license.

About eLife

eLife is a unique collaboration between the funders and practitioners of research to improve the way important research is selected, presented, and shared. eLife publishes outstanding works across the life sciences and biomedicine -- from basic biological research to applied, translational, and clinical studies. All papers are selected by active scientists in the research community. Decisions and responses are agreed by the reviewers and consolidated by the Reviewing Editor into a single, clear set of instructions for authors, removing the need for laborious cycles of revision and allowing authors to publish their findings quickly. eLife is supported by the Howard Hughes Medical Institute, the Max Planck Society, and the Wellcome Trust. Learn more at elifesciences.org.

eLife

Related Evolution Articles:

Prebiotic evolution: Hairpins help each other out
The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively.
How to be a winner in the game of evolution
A new study by University of Arizona biologists helps explain why different groups of animals differ dramatically in their number of species, and how this is related to differences in their body forms and ways of life.
The galloping evolution in seahorses
A genome project, comprising six evolutionary biologists from Professor Axel Meyer's research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse.
Fast evolution affects everyone, everywhere
Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human influences.
Landscape evolution and hazards
Landscapes are formed by a combination of uplift and erosion.
New insight into enzyme evolution
How enzymes -- the biological proteins that act as catalysts and help complex reactions occur -- are 'tuned' to work at a particular temperature is described in new research from groups in New Zealand and the UK, including the University of Bristol.
The evolution of Dark-fly
On Nov. 11, 1954, Syuiti Mori turned out the lights on a small group of fruit flies.
A look into the evolution of the eye
A team of researchers, among them a zoologist from the University of Cologne, has succeeded in reconstructing a 160 million year old compound eye of a fossil crustacean found in southeastern France visible.
Is evolution more intelligent than we thought?
Evolution may be more intelligent than we thought, according to a University of Southampton professor.
The evolution of antievolution policies
Organized opposition to the teaching of evolution in public schoolsin the United States began in the 1920s, leading to the famous Scopes Monkey trial.

Related Evolution Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#513 Dinosaur Tails
This week: dinosaurs! We're discussing dinosaur tails, bipedalism, paleontology public outreach, dinosaur MOOCs, and other neat dinosaur related things with Dr. Scott Persons from the University of Alberta, who is also the author of the book "Dinosaurs of the Alberta Badlands".