Mutation discovery could help prevent genetic disorders

Scientists from Britain and China have made a discovery that might lead to the ability to repair mutations in genes that cause harmful disorders, such as cystic fibrosis and certain cancers.

Geneticists at the United Kingdom's Oxford University and Zhejiang University in China have discovered that cells rank genes by importance, and give certain regions of our genetic make-up special treatment when repairing mutations.

Genetic mutations are one of the driving forces of evolution. They happen when a cell makes an error while copying DNA – the molecules that make up our genes. Some mutations cause no harm or even end up being beneficial, but others are responsible for illnesses such as muscular dystrophy and types of cancer.

Nicholas Harberd, a plant geneticist at Oxford University and lead author of the study, said his research suggests cells have found a way to target "important" regions of genetic material for protection against mutation, and that they focus less attention on other regions.

The study, published in the journal Genome Research, looks at a mechanism called DNA mismatch repair, or MMR, in plant cells.

During the MMR process, which occurs in cells throughout the animal and plant kingdom, an enzyme repairs parts of DNA that have been copied incorrectly during cell replication.

The scientists compared the frequency and distribution of mutations in the genome of plants that were proficient in MMR against those in a plant strain that was not able to perform MMR.

The genome is the sum of the genetic material in a cell. A minority of an organism's genome is made up of genes which code for proteins – large regions of the genome are made up of "non-coding" DNA.

The researchers found that in the MMR-deficient strain, mutations were more regular and were randomly distributed throughout the genome.

In the MMR-proficient plant genome, mutations were less regular and were not as randomly distributed. Areas of the genome that code for genes had fewer mutations than areas of the genome that do not code for genes.

"It suggests that our cells and the cells of living organisms have developed the ability to target their protection particularly to genes, rather than non-gene parts of the genome," Harberd said.

Harberd said the discovery could provide valuable information to scientists who are developing ways to eliminate harmful mutations in the human genome. Other gene editing processes found in nature – such as CRISPR – have led to technology that can alter the genome with incredible accuracy.

"From a scientific perspective, that's probably quite reasonable," Harberd said. "But that's very much in the long term, and that whole issue is fraught with ethical and legislative concerns. What's exciting is that we've come to understand more about evolution and variation. Mutation is often described as being a random process – I guess what we are suggesting is that it's somewhat less random that previously people had realized."