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Amphioxus and us
Pete Wilton | 19 Jun 08
Amphioxus is a tiny wormlike creature but it has a big evolutionary story to tell.
With its evolutionary branch poised at the divide between vertebrates and invertebrates, as our news story reports, its genome is now revealing clues to genetic events that shaped the evolution of humans and all other vertebrates.
New findings published in Nature suggest that, over 500 million years ago, our ancient proto-vertebrate ancestor duplicated its entire genome twice in two distinct events: kick-starting vertebrate evolution.
It sounds like something out of a 1950s horror movie (Night of the Mutant Vertebrates!) but Peter Holland, a lead author of the paper and head of the Oxford team who began the work in 1991, assures me that it isn't that uncommon.
‘We know that duplications of the whole genome can occur in plants and in certain amphibians,’ Peter explains. ‘In each event the doubling of the genome probably occurred within a single generation as a result of a mistake in the cell division forming our ancestor’s sex cells.'
In hindsight these may well have been brilliant mistakes; with more genes come more opportunities for evolution to act.
Susumu Ohno first suggested the idea that vertebrate genomes were shaped by ancient genome-wide duplications in 1970, yet his timings didn't add up. Now, after almost two decades of work at Oxford that saw Peter and colleagues analyse first individual genes and then entire genomes, the team has definitive evidence for two duplications.
The new research describes the 520 million base pair genome of amphioxus and compares this to the DNA of other animals, including the human genome.
So what does this mean for evolution and us? According to Peter: 'We can’t be sure but the duplication may have made it possible for some of the ‘spare’ genes to take on other functions or specialise in the development of more complex body parts. A lot of this genetic information would have been quickly lost but some survived to help make vertebrates the animals they are today.’
paper, on which the Oxford team are also co-authors, is to be published
in Genome Research. It will explore in detail the links between the
amphioxus genome sequence and specific biological phenomena.