What is virus?
Viruses are acellular microorganisms that can multiply only in living cells. Viruses are made up of nucleic acid and proteins. Viruses are dead outside the body but if they come in contact with a body, they become alive. We can collect them in the form of crystals.
History of viruses. Who discovered
Virus literally means poison, which was first discovered by Dr. Edward Jenner in 1716 to be caused by the smallpox virus. He also invented the smallpox vaccine. After this, in 1886, Aldolf Mayer scientist told that mosaic disease in tobacco plant is caused by a virus. Further, Russian botanist Dmitry Ivanovsky also started studying mosaic disease in tobacco plant in 1882. While studying, he discovered the existence of the virus. Bejrink and Bohr also observed its effect on tobacco leaves and named it tobacco mosaic virus. The reason for keeping the word mosaic was because of the mosaic-like pattern found in the leaves of the tobacco plant. Seeing this sign, scientists named the particular virus as Tobacco Mosaic Virus.
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living characteristics of viruses
- Viruses have a definite shape and form.
- Viruses reproduce and multiply in living cells.
- DNA or RNA is found in virus.
- Mutations are found in the virus.
- Viruses act like parasites.
Non-living characteristics of viruses
- We can crystallize the virus. And can be used like a normal chemical.
- Virus does not have respiration.
- Viruses can multiply only inside living cells. While outside become inactive.
- No metabolic activities are found in them.
- Viruses are acellular because they do not contain cell organelles such as cytoplasm, cell wall, and other cell organelles.
Structure of viruses
The shape of the virus can be bar shaped, sphere shaped or square shaped.
Some viruses are like threads.
There is variation in the size of the virus. The smallest virus measures 10mu while the largest virus measures up to 350mu.
Viruses are mainly made up of two parts
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| Structure of virus 🦠|
- Nucleic acid -
This part is made up of DNA or RNA which forms part of the center of the virus. The virus is infectious through this part. RNA is found in plant virus and DNA is found in animal virus.
- Protein -
The nucleic acid part of the virus is surrounded by proteins from all sides. This part is not infectious and is called protein coat. It is made up of several similar subunits called capsomeres. The capsomer is made up of several protein molecules.
Types of Viruses
- Plant virus -
These viruses spread infection on plants, RNA is found in them and cover is not found.
- Animal virus -
These viruses usually attack animals and infect them. Genetic material DNA is found in them, some viruses have envelope and some viruses do not, like mums virus and influenza virus. Whereas it is absent in polio virus.
- Bacteriophage or bacterial virus -
This virus attacks the bacteria and destroys them. Genetic material DNA is found in this virus.
Reproduction or Multiplication in viruses
The entry of virus in plants is due to the injury of insects or cells, in this process the cell wall of the host cell is cut, after which the virus enters the cytoplasm and enters inside the nucleus. After the virus enters the cytoplasm of the host cell, the protein capsid of the virus breaks down, due to which the RNA becomes free and enters the nucleus from the cytoplasm. Application inside the nucleus causes the formation of DNA first, followed by DNA. RNA begins to form from this, thus thousands and hundreds of viral RNA are formed, at the same time the proteins of the capsid are formed inside the nucleus and finally this process is completed in the cytoplasm. A protein coat is formed around the RNA from which a new virus is formed. After multiplication in the virus, either it remains in the local lesion or sometimes the virus reaches the xylem and phloem and by Rohan process reach other parts of the plant.
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