Differences Between DNA and RNA Viruses

Differences Between DNA vs RNA Viruses

Viruses are infectious biological agents that are completely dependent on the host cell in order to complete their replication process, transcription of the genome, and translation of the mRNA transcripts into proteins. Unlike most living things, the viruses do not have cells. A virus particle is made up of a core of nucleic acid, enclosed in a protein capsule. The virus genome consists of either a DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). Depending on whether they have DNA or RNA genome, viruses are classified into two categories; DNA viruses and RNA viruses. The viral DNA or RNA may be linear or circular and single or double-stranded.

DNA Viruses

The viruses with DNA genome are known as DNA viruses. Some viruses contain either double-stranded or single-stranded DNA genome. This genome can be linear or segmented. These viruses are usually large, icosahedral, enveloped in lipoproteins, and they do not have polymerase enzymes. They are cause to a latent infection. Some examples for DNA viruses are Herpes viruses, poxviruses, hepadnaviruses and hepatitis B.

RNA Viruses

Viruses with RNA in their genome are classified as RNA viruses. The RNA viruses can be further classified as single- stranded RNA viruses and double-stranded RNA viruses. Single stranded RNA viruses can be further classified into negative-sense and positive-sense RNA viruses. Positive-sense RNA serves directly as mRNA, but in order to serve as mRNA, negative-sense RNA must use RNA polymerase to synthesize a complementary, positive strand.

DNA Viruses vs RNA Viruses

• The major difference between these two types is that the RNA viruses have RNA in their genome while the DNA viruses have DNA in their genome. Both the DNA and RNA cannot be found in the same virus.

• RNA virus first adsorbs to the host cell surface. Then the attached virus fuses with the endosome membrane. Finally as a result of fusion of the viral, nucleocapsid is released into the cytoplasm. Unlike RNA viruses, DNA viruses pass their DNA into the nucleus of the host cell and not into the cytoplasm of the host cell.

• DNA polymerase enzyme is used in the replication process of DNA viruses. Since the DNA polymerase has a refining activity, the mutation level is lower in DNA viruses. RNA polymerase is used in RNA replication process of RNA viruses. The mutation level is high in RNA viruses because the RNA polymerase is unstable and can cause errors during the replication.

• In DNA viruses, there are two phases in the transcription process namely early and late transcription. In the early phase, the mRNAs are made (alpha and beta mRNA). In the late phase, gamma mRNAs are made and are translated into the cytoplasm. The late phase occurs after the DNA replication. These phases cannot be distinguished in the RNA transcription process in RNA viruses. RNA viruses translate mRNAs on host ribosomes and make all five viral proteins at once.

• RNA replication of RNA viruses usually occurs in the cytoplasm of the host cell while DNA replication of DNA viruses occurs in the nucleus of the host cell.