Virus is a kind of non-cellular organism that is small in size, simple in structure, contains only one nucleic acid (DNA or RNA), and must be parasitic in living cells and proliferate by means of replication.

Virus is a non-cellular life form, which consists of a long nucleic acid chain and a protein shell. Viruses do not have their own metabolic mechanism and no enzyme system. Therefore, the virus leaves the host cell and becomes a chemical substance without any life activity and unable to reproduce independently. Its replication, transcription, and translation capabilities are all carried out in the host cell. When it enters the host cell, it can use the substances and energy in the cell to complete life activities, and produce it according to the genetic information contained in its own nucleic acid. A new generation virus like it.

In a narrow sense, biological virus is a unique infectious agent, which is a tiny organism that can use the nutrients of the host cell to autonomously replicate its own DNA, RNA, protein and other life components. Biological viruses, whether it is a virulent phage or a mild phage, must be replicated and reproduced in a living host cell, and use the nucleotides and amino acids of the host cell to autonomously synthesize some of its own components to assemble the next generation of individuals. and achieve their goals.

The replicated biological virus lyses the host cell and is released to infect new host cells. Although biological viruses will bring certain benefits to human beings, such as the use of bacteriophages to treat some bacterial infections; the use of insect viruses to treat and prevent some agricultural pests and diseases, but they are very harmful, such as HIV, rabies virus, etc. Danger to life; influenza virus, hepatitis virus, etc. will bring disease; TMV, potato Y virus will bring property damage to people.

A virus is a tiny organism that can spread among other organisms and infect organisms (in fact, because the virus itself cannot metabolize, it cannot be said that a virus is an organism to some extent). “Viruses” are sometimes used to describe those organisms that spread and infect among eukaryotes; “phages” or “phagosomes” are used to describe those organisms that spread among prokaryotes. The origin of the virus is not very clear.

Viruses are not only divided into plant viruses, animal viruses and bacterial viruses. Structurally, it is also divided into: single-stranded RNA virus, double-stranded RNA virus, single-stranded DNA virus and double-stranded DNA virus The life process of virus is roughly divided into: adsorption, injection (genetic material), synthesis (reverse transcription/integration into the host) Cellular DNA), assembly (using host cells to transcribe RNA, translate protein to reassemble), and release in five steps. Because the virus will shorten the distance between cells, it is easy to make the cells fuse to form multinucleated cells, and then lyse.

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