Evolutionary Theory: Scientists Examine Key Aspect Of Evolution

The evolutionary theory reveals that pairs of chromosomes in asexual organisms can evolve independently from each other where they become quite different over time, known as the 'Meselson effect.' Scientists at the University of Glasgow have conducted an in-depth study of the Meselson effect in any organism at a genome-wide level, where they examined a parasite called 'Trypanosoma brucei gambiense' (T.b. gambiense).

The 'T.b. gambiense' parasite is known for causing the African sleeping sickness in humans, which has symptoms such as headaches, fever, fatigue and body aches, which do not occur until weeks or months after infection. The symptoms eventually lead to neurologic problems as the infection spreads to the central nervous system.

The researchers examined the Meselson effect in T.b. gambiense, where they gathered 85 isolates of the parasites in Guinea, Cote d'Ivoire and Cameroon, which were collected between 1952 and 2004. Similar genomes from different areas together with a lack of recombination in the evolution of the parasite indicated that the sub-species had developed from a single individual during 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," Dr. Willie Weir, lead author of the study, said in a news release. "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."

The researchers claimed that the parasites inability to recombine with each other prevents genes from being exchanged between strains. The team also found that the parasite uses gene conversion to compensate for its lack of sex.

According to the researchers, evolutionary theory indicates that asexual organisms could eventually become extinct. If this is the case with the T.b. gambiense parasite, then the majority of African sleeping sickness will come to an end. However, it is almost impossible to prove when this event would take place, according to the researchers.

The findings of this study were published in eLife.

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