Question

4a). RNA viruses often undergo rapid evolution. What aspects of their biology contribute to their high rate of evolution? What are some consequences of their rapid evolution?  

4b). What are the general features of replicative cycles of an RNA virus upon entering host cells?

4c). How is this replicative cycle different to that of a virus with DNA as genetic materials?     

Answer 1

4a). There is an high error rate inherent in the synthesis of RNA and will results in high mutation rates of RNA virus. But under stable conditions, the mutation rate will be slow. And for some favourable conditions, the virus will replicate rapidly and rapid evolution results. This rapid evolution will results in certain consequences because of the evolution of new viral infections. And this will cause a negative impact on the production of new vaccines which will be effective for the emerging disease . And the control of infections will be difficult due to these factors.

4b). The virus will enters into the cell by binding the glycoprotein present in the envelope of virus combines with the receptor of host cells. The capsid containing the viral genome enters into the cell and the capsid will gets lysed and viral genome is released. This viral genome functions as the template for the synthesis of the complementary RNA and new copies of viral genome RNA are made. The complementary RNA functions as mRNA and is translated into the capsid protein and glycoprotein. The enveloped glycoprotein is been transported to the plasma membrane by the vesicles. Capsid will gets formed around each viral genomes and new virus will gets formed.

4c). The replication of DNA virus generally occurs in the nucleus while the replication of RNA occurs in the cytoplasm. The DNA virus replicates by using host DNA - dependent RNA polymerase to produce mRNA and uses DNA dependent DNA polymerase to produce DNA from either the virus or the host.

The RNA virus gets replicated in the cytoplasm using the viral RNA- dependent RNA polymerase to produce the mRNA and the genome will gets replicated.