They defy evolutionary theory of random mutations


When DNA is damaged and not repaired, a mutation occurs, a change in the genetic sequence. Until now it was believed that the mutations were random but the results of a study by an international team of scientists have called into question this evolutionary theory.

The research, led by the University of California, Davis, and the Max Planck Institute for Developmental Biology in Germany, radically changes the understanding of evolution and in the future it could be used to grow better crops and even fight cancer, argue the authors.

“We always thought that the mutation was basically random in the whole genome but it turns out that it is very little random” and that this is the case for the benefit of the plant, says Gray Monroe, a researcher at UC Davis and lead author of the paper.

To carry out the study, the results of which were published in Nature, The researchers spent three years sequencing the DNA of hundreds of Arabidopsis thaliana, or thale cress, a small flowering plant that is used as a model because its genome is relatively small (about 120 million base pairs, compared to 3,000 million pairs of humans).

The Max Planck researchers They grew the plants in a sheltered laboratory so that defective plants that probably would not have thrived in nature could survive.

When sequencing them, they observed more than a million mutations that, contrary to expectations, followed a non-random pattern.

“At first glance, what we found seemed to contradict the established theory that initial mutations are completely random and that only natural selection determines which mutations are observed in organisms,” details Detlef Weigel, scientific director of the Max Planck Institute and lead author. of the study.

They examine the genome of the thale cress plant, which is barely 120 million base pairs long. SPECIAL

Instead of randomness, they found patches of the genome with low mutation rates that contained an overrepresentation of essential genes, as those involved in cell growth and gene expression.

“These are the really important regions of the genome,” says Monroe, the areas that are biologically most important and that are “most protected from mutation.”

They are also the areas most sensitive to the deleterious effects of new mutations and where “DNA damage repair therefore appears to be particularly effective,” Weigel points out.

Scientists found that the way DNA wrapped itself around different types of proteins helped predict whether or not a gene would mutate.

“It means that we can predict which genes are more likely to mutate than others and it gives us a good idea of ​​what is going on,” according to Weigel.

The findings are a surprising twist on Charles Darwin’s theory of evolution by natural selection because it reveals that the plant has evolved to protect its genes from mutation to ensure survival.

Knowing why some regions of the genome mutate more than others could help develop better crops and new treatments for diseases caused by mutations, such as cancer.

The amount

3 billion of base pairs has the genome of the humans, whereas the DNA of the Arabidopsis thaliana, or watercress of thale, is about 120 million base pairs.

They hope to one day apply the study to the human genome. AFP / Archive

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