Differences Between DNA and RNA Viruses

DNA viruses contain DNA as the genetic material while RNA viruses contain RNA as the genetic material. Generally, DNA genomes are larger than RNA genomes. Furthermore, most DNA viruses contain double-stranded DNA while most RNA viruses contain single-stranded RNA. These are the key differences between DNA and RNA viruses.

Viruses are infectious particles that act as obligate parasites. They depend on another living cell in order to multiply in number. They carry out their replication process, transcription of the genome, and translation of the mRNA transcripts into proteins after infecting the respective host organism. Unlike other living things, they do not have a cellular structure. Hence, they are acellular and nonliving particles that belong to a separate group. Structurally, a virus has two components: a core of nucleic acid and a protein capsule. The viral genome consists of either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). Likewise, depending on the genome, viruses can be DNA viruses or RNA viruses. Furthermore, DNA can be either single stranded or double stranded; it can also be linear or circular.

CONTENTS

1. Overview and Key Difference
2. What are DNA Viruses
3. What are RNA Viruses
4. Similarities Between DNA and RNA Viruses
5. Side by Side Comparison – DNA vs RNA Viruses in Tabular Form
6. Summary

What are DNA Viruses?

DNA viruses are viruses that contain DNA genomes. Some viruses contain double-stranded DNA genomes while some contain single-stranded DNA genome. Hence, they belong to group 1 and group 2 of Baltimore classification. Furthermore, this genome can be linear or segmented.

Moreover, these viruses are usually large, icosahedral, enveloped in lipoproteins, and they do not have polymerase enzymes. Whenever they replicate, they use either host DNA polymerases or virally encoded DNA polymerases. Moreover, they cause latent infections. Some examples of DNA viruses are Herpes viruses, poxviruses, hepadnaviruses, and hepatitis B.

What are RNA Viruses?

RNA viruses are viruses with RNA in their genomes. These viruses can be further classified as single-stranded RNA viruses and double-stranded RNA viruses. However, most RNA viruses are single-stranded and they 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 an RNA polymerase to synthesize a complementary, positive strand.

RNA viruses belong to group III, IV, and V of the Baltimore classification. Group III includes double-stranded RNA viruses while group IV includes positive-sense single-stranded RNA viruses. Finally, group V includes negative-sense ssRNA viruses. In addition, retroviruses also have a single-stranded RNA genome, but they transcribe via an intermediate of DNA. Hence, they are not considered as RNA viruses. Rhabdovirus, coronavirus, SARS, poliovirus, rhinovirus, hepatitis A virus, and influenza virus, etc., are some examples of RNA viruses.

What are the Similarities Between DNA and RNA Viruses?

• DNA and RNA viruses are obligate parasites; hence, they need a living cell to replicate.
• Also, they are infectious particles.
• Thus, they cause diseases to human, animals, bacteria, and plants.
• Besides, both types have single stranded and double stranded genomes.
• And, they can be naked or enveloped viruses.
• Furthermore, they contain protein capsids.
• Both DNA and RNA cannot be found in the same virus.

What are the Differences Between DNA and RNA Viruses?

DNA viruses have DNA in their genome while RNA viruses have RNA in their genome. Unlike RNA viruses, DNA viruses pass their DNA into the nucleus of the host cell and not into the cytoplasm of the host cell. But RNA virus is first adsorbed to the host cell surface, fuses with the endosome membrane and releases the nucleocapsid into the cytoplasm. Hence, these are the key differences between DNA and RNA viruses.

Furthermore, 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. On the other hand, 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. Therefore, this is an extremely important difference between DNA and RNA viruses.

In DNA viruses, there are two phases in the transcription process as early and late transcription. In the early phase, the mRNAs are made (alpha and beta mRNA) while in the late phase, gamma mRNAs are made and are translated into the cytoplasm. The late phase occurs after 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. Therefore, this is one of the significant differences between DNA and RNA viruses. Most importantly, 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.

The below info-graphic lists out the differences between DNA and RNA viruses.

Summary – DNA vs RNA Viruses

DNA viruses and RNA viruses are the two main categories of viruses. As their names imply, DNA viruses contain DNA as their genetic material while RNA viruses contain RNA as their genetic material. Thus, this is one of the key differences between DNA and RNA viruses. Generally, DNA genomes are larger than RNA genomes. Furthermore, most DNA viruses contain double-stranded DNA while most RNA viruses contain single-stranded RNA. DNA viruses show accurate replications while RNA viruses show error-prone replication. Apart from that, DNA viruses are stable and show a lower mutation rate while RNA viruses are unstable and show a higher rate of mutation. This is the summary of the differences between DNA and RNA viruses.

Reference:

1. “DNA Viruses.” NeuroImage, Academic Press, Available here.
2. “RNA Virus.” Wikipedia, Wikimedia Foundation, 20 Feb. 2019, Available here.

Image Courtesy:

1. “Tevenphage” By Adenosine (original); en:User:Pbroks13 (redraw) – http://commons.wikimedia.org/wiki/Image:Tevenphage.png (CC BY-SA 2.5) via Commons Wikimedia
2. “SARS Virus Particles” By NIH Image Gallery (Public Domain) via Flickr