Epidemologist explains why COVID-19 mutations shouldn’t scare you
Mutating coronavirus
DNA, or in the case of the coronavirus, RNA, is the set of genetic instructions that tell an organism which bricks are needed and in what order to create the proteins it needs to survive.
Mutations affect these instructions, meaning the number or type of amino acids that make up a particular protein get changed. This, in turn, has the potential to change the properties of the protein. However, this is the Hollywood spoiler: most mutations lead to no beneficial change in the protein properties at all. In fact, mutations that change the properties of a protein are more likely to weaken the virus than strengthen it.
Only mutations that confer an advantage (or make no difference) persist in the DNA. To talk of the virus having “aims” and “intents” with mutations is to talk from a human perspective. In a similar way, there is a debate about whether the “ultimate virus” would be one that survived within you undetected for your entire life, or one that hops quickly and easily between new hosts. Both would require extensive mutations, the results of which are too random to be planned.
Proteins are folded into extremely complex 3D shapes, depending on the interactions between amino acids in the same string. Changing an amino acid that is key to holding the shape together, such as swapping a positively charged one for a negatively charged one, will change that shape.
Those billions of years of molecular sculpting that allow proteins to be just the right shape to cooperate are not compatible with sudden mutations and radically different shapes. No additional abilities, no superpowers – typically the protein just no longer fits as it should. And if that protein is key to the virus infecting you? Good news! That particular virus particle can’t harm you and that mutated virus version dies out.
So how does any organism, human or virus, keep going if most mutations are bad for it? A common approach is to go back and fix the mutation.
When administering its system of turning the DNA code into strings of amino acids to make a protein, evolution has built in some steps to check for changes. If you have spent billions of years refining your blueprint then you want some protection for all of that previous hard work. Therefore, both humans and the coronaviruses have correction mechanisms for their DNA/RNA templates.
This evolutionary proofreading is there to correct the “errors” that would change proteins and inhibit the virus. The proofreading also reduces the speed at which advantageous mutations are acquired.
Not all amino acids are important to the shape, and changing them doesn’t alter the protein. The mutations most commonly found in the coronavirus spike protein that have made it through and become established are in the group of “no significant change to the protein:”swapping one large amino acid for another large amino acid. The biological equivalent of putting different tires on your car. While these amino acids are different, the spike protein seems largely unchanged in how it works. No better or worse at getting inside cells.
Viruses work through generations far faster than large organisms such as ourselves, and groups of small changes can cluster more quickly into significant differences. However, in the case of the newly identified variant in the south-east of England, we have no evidence yet that this mutation makes the virus more harmful or transmissible.
This article byMatt Webster, Head of the School of Allied Health,Anglia Ruskin Universityis republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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