A team of scientist from the Universities of Bath and Birmingham have made a discovery that is making noise in the world of Biology. Ironically, they had the realization while studying silent mutations in DNA. What they found is a new method of evolution. Well not a new method per say as the scientists predict this method is being used in all forms of life; however, new in the sense that it was only recently realized. What they have discovered is a trend of tangles in DNA strands. This tangling occurs in DNA strands that are not in a double helix as DNA typically is. However The DNA strands are separated during copying. This task is done by DNA polymerase enzymes. During the copying process, the enzymes are often disrupted by the tangles in the strand. The resulting skipping of genes causes specific mutations to the DNA.
The scientists then tested their hypothesis by way of experiment. They did so by studying the evolution of soil bacteria called Pseudomonas fluorescens (SBW25 and Pf0-1). They began by removing the gene that give the bacteria the ability to swim. They then observed the re-evolution of the strains to regain the ability swim. Both strains evolved quickly; however, there was a clear differences in predictability. One strain (SBW25) mutated the same part of a particular gene in every trial. The other strain (Pf0-1) varied in which gene and where the mutation occurred in each trial. Upon further observation, this contrast coincided with a hair-pin shaped tangle in the SBW25 strain. As the DNA polymerase enzymes would pass this tangle they would be effected in a predictable manner that would disrupt copying of DNA and result in a mutation that allows for the bacteria to swim. The scientists tested the theory by removing the tangle. They did so using 6 silent mutations so that the DNA sequence would not have a relevant change. The trials after the change showed that both strains showed inconsistent areas being mutated.
DNA are the dictators of protein synthesis in the body. The DNA sequences code for the types of proteins that are created. Proteins perform many of the bodies function. This means that even the slightest change in the sequencing of DNA can have major effects on the functioning of a human body or any organism. The process of evolution was thought to be caused by random errors in DNA sequencing that coincidentally gave an organism a survival advantage. These mutations would then be tested in the concept of survival of the fittest. While this is still thought to be the most prevalent form of evolution, especially with eukaryotic organisms, the tangling of DNA strands proposes a form of evolution that would be easier to study and predict.
The predictability of such a phenomenon is where the intrigue in viruses arises. “If we knew where the potential mutational hotspots in bacteria or viruses were, it might help us to predict how these microbes could mutate under selective pressure.” says Dr. Tiffany Taylor, from the Milner Centre for Evolution. Mutational hotspots have already been found in cancer, and the new information on their significance is getting scientists excited about the opportunities present. The new ways to understand and predict evolution of bacteria and viruses may allow scientists to be a step ahead on vaccines and be able to anticipate and understand new variants. It’s hard not to think this information would’ve been nice before the rise of SARS-CoV-2.