An artist's interpretation of a double-stranded helix. The image is from Shutterstock.
New research suggests that genetic changes may not be random. One of the key assumptions of the theory of evolution would be upended by that.
Researchers studying the genetic changes in a common roadside weed, thale cress, have discovered that the plant can shield the most "essential" genes from the changes, while leaving other sections of its genome to build up more alterations.
Grey Monroe, a plant scientist at the University of California, Davis, told Live Science that he was surprised by the non-random mutations they discovered. I have been told since high-school biology that there are random changes.
Unraveling the human genome is related.
The theory of evolution by natural selection states that random mutations give rise to changes that affect survival. The first step in evolution by natural selection was assumed to be random. The new study suggests that this may not be true.
Monroe said that the idea of randomness in biology has been around for over a hundred years and is easy to take for granted. I had never questioned the idea as a practicing geneticist and evolutionary biologist.
The new finding does not undermine the theory of evolution, and the researchers said randomness still plays a big role. The study shows that the genetic alterations are more complex than previously thought.
There are mistakes with the DNA.
There are a lot of chances for genetic errors to occur.
The DNA in a single cell can be damaged between 1,000 and 1 million times a day. Each time a cell divides, it has to be copied.
Our cells are able to counteract a lot of this damage. Monroe said that the cells are constantly working to correct their genes and have evolved complex machines to make repairs.
DNA repair proteins can't fix all mistakes. Monroe said that if damage or copying errors are not repaired, they cause a change in the DNA sequence.
There are two main types of genes, germline and somatic, which can't be passed on to offspring. Germline mutations are what fuel evolution by natural selection and become more or less common in a population based on how they affect the carrier's ability to survive.
Some of the genes have the potential to change the chances of survival. Major changes to an organisms are only possible when the genes that code for it are damaged. Monroe said that most of the human genome is made of non-gene DNA.
There is a non-random pattern.
Researchers decided to test the randomness of the mutations by looking at the genomes of thale cress to see if there were any differences between the genes and non genes.
Thale cress has a small genome, which makes it easier to sequence the plant's genes. Monroe said that it has a short life span and that it can quickly accumulate multiple generations of mutations.
Hundreds of plants were grown in a laboratory for three years. The researchers found more than 1 million genes. The parts of the genomes containing genes had lower rates of mutation than the non-gene regions.
Thale cress is a model for studying genetic changes because of its small genome and short lifespan. The image is from the Pdraic Flood.
Monroe thinks that other organisms could also have non-random genetic changes. We are following up with our study by looking at the question in other species and finding results that suggest non-random mutation isn't unique to Arabidopsis.
The level of non-randomness may not be the same for different species.
The essential genes are protected.
There is a defensive mechanism in place to prevent potentially disastrous mutations, according to the non-random pattern in the genes and non-gene regions.
Monroe said that in genes coding for proteins essential for survival and reproduction, the most likely to have harmful effects are the mutations. The results show that genes and essential genes in particular have a lower mutation rate than non-gene regions. The result is that offspring have a lower chance of being harmful.
Researchers found that essential genes send signals to repair their own genes. This signaling is done by histones, which are specialized genes in the DNA.
Monroe said that the results of the study showed that the most biologically essential genes are wrapped around histones with chemical marks. The chemical marks are believed to be signals to promote DNA repair.
Monroe said the idea of histones having unique markers is not new. There are chemical markers that can affect whether or not a DNA repair proteins fixes a problem properly.
This is the first time that these markers have been shown to influence genome-wide patterns of mutations.
There are potential implications.
The researchers hope to use their findings to improve human medicine.
"Mutations affect human health in many ways, being a cause of cancer, genetic disease and aging," Monroe said. He said that being able to protect certain parts of the genome could help prevent or treat problems.
More research is needed before researchers can tell if the same non-random mutations occur in humans. Monroe said that their discoveries were made in plants and did not give rise to new treatments.
Monroe said that the researchers think the chemical signals given off by essential genes could be used to enhance gene-editing technologies that could help us create crops that are more resilient to climate change.
The study was published in the journal Nature.
Live Science published the original article.
All Rights Reserved © 2024
