IMMUNOLOGY

Detailed explanation-1: -RNA viruses have high mutation rates-up to a million times higher than their hosts-and these high rates are correlated with enhanced virulence and evolvability, traits considered beneficial for viruses.

Detailed explanation-2: -As a virus replicates, its genes undergo random “copying errors” (i.e. genetic mutations). Over time, these genetic copying errors can, among other changes to the virus, lead to alterations in the virus’ surface proteins or antigens.

Detailed explanation-3: -RNA viruses are characterized by high mutation rates compared with most DNA systems (1), due mainly to the lack of exonuclease proofreading activity displayed by their RNA polymerases (2).

Detailed explanation-4: -Positive-strand RNA viruses have genetic material that can function both as a genome and as messenger RNA; it can be directly translated into protein in the host cell by host ribosomes.

Detailed explanation-5: -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.

Detailed explanation-6: -Human diseases causing RNA viruses include Orthomyxoviruses, Hepatitis C Virus (HCV), Ebola disease, SARS, influenza, polio measles and retrovirus including adult Human T-cell lymphotropic virus type 1 (HTLV-1) and human immunodeficiency virus (HIV).