When DNA Crosses the Species Barrier – Science et Avenir

This article is taken from Les Indispensables de Sciences et Avenir #210 July/September 2022.

We inherit genes from our parents, it is something acquired. What if we also stole some from the neighbors? Geneticists call “horizontal transfer of genetic material” the fact that DNA is recovered from people other than their ancestors. This phenomenon is well documented for bacteria that frequently exchange chromosomes: thus, it is easier for them to adapt to changes in the environment or to the presence of antibiotics, which increases antibiotic resistance.

A unique example of gene transfer between vertebrates

But horizontal transfer is not limited to microorganisms. In 2021, researchers at Queen’s University in Canada found that Atlantic herring shares the same antifreeze protein… with two species of smelt! It is no coincidence that they inherited it from a common ancestor, a study of their phylogeny shows. Thus, the herring appears to have passed on its gene to smelt by horizontal transfer. To date, the example is unique among vertebrates. And when it comes to fish, it is no coincidence.

“Probably, in the aquatic environment, this process proceeds more easily than on land,” says Clement Gilbert, an evolutionary geneticist at CNRS, “because fish reproduce by external fertilization: males and females throw out their gametes, which form an egg directly on contact with it “. average.

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