Retrovirus vs Virus
Viruses are the first biological structures observed from an electron microscope, since they were not visible under the light microscope. They are the smallest living organism and do not have a proper cellular structure. Viruses need living organism to reproduce, and called obligate endoparasites (Taylor et al, 1998). They are not either living or nonliving organism and held in between.
Viruses are the host specific, and out of the cell they are metabolically inert. Virus causes diseases to animals, plants, and bacteria. Most common virus diseases are rabies, influenza, HIV, and H1N1 etc.
Virus contains DNA or RNA as their genetic material and DNA or RNA may be single stranded or double stranded. The core of viruses i.e. genetic material is surrounded by protein or lipoprotein coat. It is called as the capsid, and sometimes the capsid is enveloped with a membrane, when they are in the outside of a cell or host. Capsid is composed with identical units, which are called capsomeres. The capsid is symmetrical and varied from simple helical form to highly complex structures.
Viruses get attached to the host cell and insert their genetic material into the host cell. In the host cell, it produces several copies of genetic material and the protein coat. These protein coats and genetic materials are assembled into new daughter viruses. If DNA is the genetic material, it can be inserted in to genome and produce more and more viral protein instead of proteins of host. All these actions occur in lytic phase. Some viruses can be dormant in the host cell and does not show any symptoms, so called lysogenic phase.
Viruses that carry reverse transcription are called retroviruses. This virus can convert their RNA into DNA copy. This process is catalyzed by reverse transcriptase enzyme. Then this DNA is integrated covalently into the host genome using integrase enzyme, which is coded by reverse transcriptase. So, retrovirus has a special advantage as a gene carrier. They are integrated into the host genome directly, but the reverse transcription is much faster than the normal transcription process and it is not much accurate. So offspring may be genetically different from the first generation. Retroviruses can cause HIV and number of cancers in animals.
What is the difference between Virus and Retrovirus?
• Retroviruses are a group of viruses, so retroviruses carry special characteristics, which are not seen in viruses.
• Virus contains genetic material as DNA or RNA but retrovirus contains only RNA.
• If the virus has DNA, it inserts DNA into the host cell, and it is integrated directly into the host genome at the lytic phase, whereas retrovirus has RNA as its genetic material and needs to convert RNA to DNA before insert it into the host genome.
• So, viruses have transcription process, whereas retroviruses have reverse transcription process.
• The second generation of the retrovirus may be different from the first generation because of the inaccuracy of the revere transcription process, whereas mostly the second generation is similar to first generation genetically since the virus has normal transcription process which is accurate than the reverse transcription.
• Because of the vast genetic change in second generation of retroviruses, treatments for diseases caused by them are difficult, than the treatments for virus caused diseases. For an example, HIV does not have such specific treatment, whereas virus diseases have treatment like rabies or influenza.
Taylor, D.J., Green N.P.O., Stout, G.W., (1998), Biological Science. Cambridge University Press, Cambridge.