Question

Why do RNA viruses appear to have higher rates of mutation?

Answer 1

Answer:

B) Replication of their genomes does not involve the proofreading steps of DNA replication.

Explanation:

RNA viruses have upto 1 billion time higher mutation rate than their host. As RNA is more fragile than DNA so these mutations are associated with the adaptability of RNA viruses in changing environment as well with their virulence. The higher mutation rates in RNA are the consequences of following factors.

• The DNA of eukaryotes as well as of some viruses have the proofreading mechanism to repair mutations. Even some very high RNA viruses also poses this ability. But most of the viral RNA polymerases lack the ability of proofreading i. e. it cannot rectify the replication errors in RNA. It causes the higher mutation rate in viral RNA.
• Another comparatively small cause is the presence of uracil base in RNA instead of thymine. Sometime cytosine base changes to uracil and this is detected in DNA because DNA don't contain uracil while it cannot be detected in RNA because it already contains uracil.

Answer 2

Answer:

B) Replication of their genomes does not involve the proofreading steps of DNA replication.

Explanation:j

1. This is because RNA polymerase do not proofread proteins or polymerase components to check for errors and repair.

2.Because RNA viruses usually encoded their replication machinery, therefore they  have the ability to  replication at high rate   which  increases chances  for  mutation, to any length and  extent to  suits their needs.

Therefore,since there is no check for the number of replication  they can go through and  no need for correction of  replication errors, they have rapid chances for  mutation  and therefore virulence. Different  offspring, with distinct genetic composition  from wrong bases insertion and translation and therefore of  virulence   totally different from  the parents will be produced. Thus mutagensis, and virulence continues to increase.