In their research paper – Population genomics reveals the origin and asexual evolution of human infective trypanosomes– Macleod et al. discuss how they have proved a key aspect of evolutionary theory, which 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’.
Dr. Annette Macleod and her team studied a parasite calledTrypanosoma brucei gambiense(T.b. gambiense), which is responsible for causing African sleeping sickness in humans. In order to demonstrate the Meselson effect inT.b. gambiense, the team sequenced the genomes of 85 isolates of the parasite, including multiple samples from disease focus points within Guinea, Côte 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.
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.
Examples of media coverage featuring the research can be found below:
- Sex life of sleeping sickness parasite may lead to its downfall (Yahoo! News)
- African sleeping sickness parasite 'has not had sex in 10,000 years' (The Independent)
- Sleeping Sickness Parasite May Become Extinct Because It Won't Have Sex (IFLScience)
- African sleeping sickness parasite 'has not had sex in 10,000 years' (The Times of India)
- Sex life of sleeping sickness parasite may lead to its downfall (Reuters Africa)