Challenge 4: How do mutations cause viral evolution?
- I can describe relationships between mutations and viral evolution.
- I can provide evidence for how viral evolution affects the ability of a virus to infect its host.
Read & Evaluate:
Mutations involve changes to the sequence of an organism’s genetic code. As you have learned, viruses typically mutate more rapidly than human cells do. This is because human cells have mechanisms to proofread the genome and also mechanisms to repair a sequence if an error is detected. Mutations can vary in severity from having zero consequence to majorly altering a protein and its function. Mutations can involve the substitution of one DNA base to another, a G for an A for instance. Or mutations can involve the insertion of additional DNA bases or the deletion of existing DNA bases. Once a mutation occurs, if it changes the function of a resulting protein, a virus or organism is then changed. Because cells and viruses interact with the environment or surrounding cells, this change is either going to give the mutated cell or virus an advantage, allowing it to thrive more easily in its environment, or will make it disadvantaged, making it more difficult to survive. This is a process called natural selection. If the mutation confers an advantage, the mutated sequence then spreads within a population and if the mutation confers a disadvantage, the mutated sequence dies out.
Consider the following scenarios (actual or hypothetical) and decide if the mutation in SARS-CoV-2 virus will be detected in an increasing portion of the population of viruses or will not be detected. Explain your answer choice.
- A mutation in the gene coding for the SARS-CoV-2 capsid proteins. The mutated proteins prevent the capsid from forming.
- A mutation in the gene coding for the spike protein responsible for recognizing the ACE2 receptor on the host cell. This mutation changes the spike proteins slightly so that they interact more loosely with the ACE2 receptors.
- A second mutation in the gene coding for the spike protein responsible for recognizing the ACE2 receptor on the host cell. This mutation makes the spike proteins a different completely different shape.
- A mutation in the gene that codes for the enzyme that copies the RNA genome of SARS-CoV-2. The mutation causes the enzyme to work at a faster rate.
- A mutation in the SARS-CoV-2 RNA genome that changes the RNA molecule so that the ribosomes no longer recognize it.
Reflect & Discuss :
- Why are RNA viruses more likely to mutate than those that have genomes made of DNA?
- What would happen if a virus that infects humans mutates and becomes more deadly to people? Would this virus continue to be a threat to the human population?