Virology deals with a study of various types of viruses including agents, submicroscopic, parasitic particle of genetic material that are present in the protein coat.


Virology is a stream of science that mainly focuses on its aspects such as their immunity, the ability to destroy or infect the host cells, their evolution, classification, structure, composition, several ways of infecting, different ways of culturing them, their use in laboratory, various methods to isolate them and their physiology.

Types of Virus

Depending upon the type of nucleic acid viruses are classified as follows:

Reverse Transcribing Viruses:  RT-Reverse Transcribing Viruses is an enzyme that is used in the generation of cDNA – Complementary DNA. One of the common examples includes hepadnaviral which falls into the category of hepatitis B viruses.

The various activities of RT are pertaining to mobile genetic elements and some replication of chromosome ends. They mainly perform three types of activities such as  DNA Polymers Activity which is dependent on DNA, secondly ribonuclease H and finally DNA Polymers Activity which is dependent on RNA.

These sequential biochemical activities are used to convert RNA into DNA in a laboratory which can penetrate into the host genome leading to viral infected diseases that are difficult to uproot.

RNA Viruses: These are the viruses that comprise of RNA as a genetic material. They can either be a single-stranded or a double-stranded RNA. These viruses have been categorized into Group 3, Group 4 and Group 5. Some of the diseases caused by them to humans include common cold, hepatitis c, polio, West Nile fever, influenza, SARS, and measles.


Mutation rates are higher for RNA viruses. It may be considered as a one of a reason for lacking back in preventing effective vaccines in preventing diseases caused by these viruses. Double standard viruses comprise of distinct viruses that differ widely based on host viruses such as fungi, bacteria, genome, virion, and organization.

A single-stranded RNA are categorized based on senses that are positive sense or negative sense. Positive-sense RNA is similar to mRNA. They are usually translated into host cells. Negative-sense RNA must be converted into positive sense RNA before translation using RNA polymerase.

DNA Viruses: These are the viruses that comprise of DNA as a genetical material. They are DNA dependent and they replicate using DNA polymerase. There is usually a double standard but in some cases, they can either be single-stranded DNA. They are categorized into Group one and Group 2 based on Baltimore classification.

Viral Disease

One of the factors that make the study of virology interesting is the diseases caused by them. Some viruses called oncoviruses which lead to the certain form of cancers. The most common among them is cervical cancer and liver cancer. Measles, rabies, herpes, common cold, diarrhea are some of the diseases that are commonly caused by viruses.

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Practise This Question

Regarding the assertion and reason, select the right option.

Assertion (A): Endosperm development precedes embryo development.

Reason(R): Endosperm provides assured nutrition to the developing embryo.