DNA Mutations Are Not Completely Random, Claims New Study

Thales Cress being grown. Image Credit: Tomas Vynikal/Shutterstock.com

Researchers may have discovered something very important about how mutations arise in DNA – while thought for a long time to be random, they appear to have a sort of pattern, not just happening following the whims of fate. This approach is actually beneficial to the survival of the species, in this case, a plant called thale cress (Arabidopsis thaliana).

Thale cress is a small flowering weed, often found on the roadside in Eurasia and Africa. It is also a favorite of plant scientists, being used to investigate genetics thanks to its relatively small genome of 120 million base pairs. That might seem big, but it is relatively small compared to other organisms. Bananas have more than four times as many base pairs, and humans 25 times as many.

As reported in the journal Nature, the team let hundreds of thale cress plants grow in the lab, where genetic defects wouldn’t impede their survival like if they were in the outside world. Sequencing these plants revealed over one million mutations across the specimens – but the mutations happened in specific areas of DNA and not in others.

“We always thought of mutation as basically random across the genome,” lead author Professor Grey Monroe, from UC Davis Department of Plant Sciences, said in a statement. “It turns out that mutation is very non-random and it’s non-random in a way that benefits the plant. It’s a totally new way of thinking about mutation.”

The team observed parts of the genome with low mutation rates, and those parts were the ones that had more essential genes such as those involved in cell growth and gene expression. The crucial finding is that the more important and sensitive areas were less likely to experience radical mutations.

“At first glance, what we found seemed to contradict established theory that initial mutations are entirely random and that only natural selection determines which mutations are observed in organisms,” added senior author Detlef Weigel, scientific director at Max Planck Institute.

It appears that the way DNA was wrapped around proteins could be used to predict if a gene was likely to mutate or not. This suggests that genomes have ways to protect the important genes from mutations, increasing survival.

“The plant has evolved a way to protect its most important places from mutation,” Weigel said. “This is exciting because we could even use these discoveries to think about how to protect human genes from mutation.”

The potential applications are very exciting. In agricultural fields, this might inform plant breeders that rely on genetic variation how to get better crops. It might also instruct ways to deal with health conditions such as cancer that are caused by genetic mutations.

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