ROLE OF MUTATION IN EVOLUTION

                                                                                          (Prepared by:Priya Prakash, 20220901007)

Viral evolution is driven by the accumulation of genetic changes, which can lead to the emergence of new strains or subtypes of the virus. Mutations play a significant role in viral evolution. Mutations can affect various aspects of viral biology, such as virulence, transmission, and host range, and can also lead to drug-resistant strains. Understanding their impact is essential for developing effective strategies to control viral infections.

But what’s Mutations in Viruses?

               Mutations are the basis for evolution and natural selection. An alteration in the genetic material (the genome) of a cell of a living organism or of a virus that is more or less permanent and that can be transmitted to the cell’s or the virus’s descendants is known as Mutation. Viruses have high mutation when compared to any life form. This helps it to rapidly evolve and adapt quickly to the host system. 

Are Mutations Good For Viruses?

                      Mutations in viruses, when they make copies of themselves can be both beneficial and harmful. Some such changes can lead to efficient reproduction or lead to dead ends or harmful outcomes which limit an organism’s ability to survive. We all know that there was once confusion on whether viruses should be considered as living or non-living organisms. But their mutation ability was considered as the most compelling arguments for viruses to be classified as living organisms.

But Why Mutations?

                    Mutations help viruses to be more effective than the previous generation in moving from host to host, speed up reproduction and thereby extend its life. It also helps them to be more effective in adhering to host surfaces. The example for this is quite well known, the spike protein of COVID-19. Mutations also have the ability to increase the probability of viruses evading the immune responses and vaccines.  

                      The illustration below depicts how mutation happens in a virus.

Let’s discuss about variations in genes due to mutations.

                   Genetic variety is produced by viral mutations but comes under the pressure of selection and random genetic drift which is directly influenced by the number of virus populations. Large populations will exhibit selection more frequently and less frequently than small populations. Thus, harmful alleles will be successfully eliminated from the population while adaptive alleles will have a chance to rule the community. Random effects, however, could mask the effects of selection in small populations. The population's frequency of mildly harmful alleles may unexpectedly increase under these circumstances, while adaptive alleles could accidentally disappear.

                  The abundance of mutants, which is also referred to as a "quasispecies," has the capacity to encode viruses with increased treatment resistance or the capacity to elude neutralising antibodies produced by the host. This challenges efforts to develop efficient vaccinations since evolution has the potential to significantly expand the number of virus serotypes that are present in human populations. In addition, viruses' special capacity for change enables them to pass over barriers separating species, leading to zoonotic diseases [1].

                    The mutation together with selection will determine which mutations will survive in the viral population.

Have you heard about Lethal Mutagenesis?

                         Lethal mutagenesis is a phenomenon in which an increase in the mutation rate of a virus or other pathogen leads to its extinction. It has been proposed as a potential therapeutic approach for treating viral infections, including those caused by HIV, influenza, and hepatitis C. However, there are many challenges associated with implementing this approach, such as balancing selective pressure on the virus with the potential for it to evolve resistance, and concerns about the safety and efficacy of the mutagenic agents themselves [2].

References

[1] R. Sanjuán and P. Domingo-Calap, “Mechanisms of viral mutation,” Cellular and Molecular Life Sciences, vol. 73, Mar. 2016, doi: 10.1007/s00018-016-2299-6.
[2] A. Stern and R. Andino, “Chapter 17 - Viral Evolution: It Is All About Mutations,” in Viral Pathogenesis (Third Edition), Third Edition., M. G. Katze, M. J. Korth, G. L. Law, and N. Nathanson, Eds. Boston: Academic Press, 2016, pp. 233–240. doi: https://doi.org/10.1016/B978-0-12-800964-2.00017-3.