State any one reason to explain …

A virus is a small parasite that cannot reproduce by itself. Once it infects a susceptible cell, however, a virus can direct the cell machinery to produce more viruses. Most viruses have either RNA or DNA as their genetic material. The nucleic acid may be single- or double-stranded.

When the genetic material is single-stranded RNA then it is the RNA virus.

The viruses that have DNA as genetic material are the DNA viruses. They have the mechanism related to the replication of the DNA and the enzymes. The DNA replication enzyme DNA polymerase has a special quality that is the proofreading which prevents the mutations as it eliminates them. whereas in the RNA viruses they don't have this property as they have RNA polymerase and they dot have his tendency and thus the mutation is faster.