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Extreme mutation – what happens then?

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About 100 million years ago, the mother of all salmonid fish underwent a doubling of all its genetic material and ever since then it has had double sets of genes. How has this affected the ability of salmonids to evolve new adaptations?

Extreme mutation – what happens then?

Nature is teeming with variety. This diversity of species, adaptations and life strategies is based on differences in DNA – the genetic code.

How do new characteristics occur?
If we want to understand how biodiversity and new adaptations arise, we also need to understand how new DNA variations occur through mutations and how such new code variations give rise to new functions.

These differences could lie in the sequence of the DNA code and how DNA is organised into chromosomes, or how the different cells and organisms use the code.

Doubling of genetic material
One of the most spectacular ways in which genetic material can be altered is by spontaneous duplication of all the genetic material. Each gene gets a copy of itself on a different chromosome. Obviously, this type of mutation is very rare, but when it happens, it can have a major impact on the evolution of new characteristics and species. At least, this is what people have believed until now.

The idea is intuitive: when one gene becomes two, one of the copies can retain the original functions, while the other copy can freely accumulate mutations and alter functions. This in turn creates lots of new genetic variation that constitute the raw materials for new adaptations.

Consequently, one key hypothesis in the field of evolutionary biology is that the duplication of genetic material causes new adaptations to evolve more rapidly, although never tested and verified in empirical studies. Is it correct? Do double sets of genes create lots of new characteristics and adaptations? The answer to this question is the goal for this project.

Salmon versus pike
The researchers will use salmonid fish, which underwent a whole genome duplication 100 million years ago, as a model system to test if there is a link between genome duplication and the evolution of new genetic functions and adaptions.

New statistical methods and bioinformatics will identify how the duplicated genes of salmon are used in different organs, and these results will afterwards be compared with other fish in the same family, including pike, which do not have an extra set of genes. In this way, it may be possible to measure whether or not gene duplication in itself increases the likelihood of developing new genetic functions and adaptations.

Computer results will be put to the test
Finally, modern gene editing technology (CRISPR) will be used to test the results of the researchers’ computer calculations.

This will be done by deleting duplicate genes that are believed to have contributed towards new functions and then checking to see if this affects the physiology of the fish. The project will focus specifically on new gene functions that are involved in metabolism in the liver.

In the laboratory, pieces of liver from the genetically edited fish can be kept alive in petri dishes for several weeks. Consequently, they can give the same liver different combinations of “food” and perform very detailed measurements in order to test whether or not, or how, the function of the liver is altered when two gene copies become one again.

The results of this project will provide us with an entirely new understanding of how the extreme form of DNA mutation – whole gene duplication – is helping to facilitate the evolution of new characteristics and adaptations.

Published 9. February 2018 - 14:19 - Updated 14. February 2018 - 9:18

Norwegian University of Life Sciences (NMBU)

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