Virus Life Cycle: Introduction, Overview, Stages, Types, Life Cycle, FAQs

Viruses can reproduce only within a host cell. The parental virus gives rise to numerous viruses, usually genetically and structurally identical to the parent virus. The mode of action of the virus depends both on its infective tendencies toward a specific host cell and on environmental conditions. In the life cycle of viral infection, the multiplication of progeny viruses is rapid. This cycle of infection often results in the death of the cell and the release of many virus progeny.

This Story also Contains

1. The Virus Life Cycle- Lytic Cycle
2. The Virus Life Cycle- Lysogenic Cycle
3. Facts on Coronavirus

Viral infection does not always result in cell death or tissue injury; in fact, most viruses lie dormant in tissue without ever causing pathological effects, or they do so only under other, often environmental changes. It's important to know about the virus life cycle, and virus reproduction represents an important part of biology.

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The Virus Life Cycle- Lytic Cycle

The following points explain how viruses infect a host cell, replicate using the cell’s machinery, and spread to other cells. Understanding the steps of the virus life cycle helps us learn how viruses cause diseases.

Attachment

The attachment of the virus to a host cell is the first step of the life cycle of a virus. This step is selective because only cells with the receptors on their surfaces can be infected by a virus. It is like how only keys that fit into existing locks can be used for opening locks.

The surface proteins of the virus bind very strongly to these receptors. Without this step, the virus cannot get inside the cell or begin virus production. This determines which organisms or tissues the virus can infect.

Entry

After attachment, the virus enters the host, another stage of the virus life cycle. The way entry occurs depends on the kind of virus. Some viruses fuse their outer envelope with the host cell membrane, while others are engulfed by the cell through endocytosis.

Others introduce their genetic material through direct injection into the cell. This entry is an important step in the initiation of virus reproduction because it enables the virus to introduce its blueprint of genetic material into the cell to hijack the machinery of the cell.

Replication (Virus Reproduction)

Replication is the heart of virus reproduction within the virus life cycle. Once inside the host cell, the viral genetic material takes control of the machinery of the host cell and starts making copies of itself. Most DNA viruses penetrate the nucleus, using that cell's DNA-replicating enzymes.

The majority of RNA viruses replicate in the cytoplasm. The host cell will have no clue that it is being given orders on what it should do as it goes through the process of producing thousands of copies of the viral genome and all its proteins. This stage ensures that the virus can replicate and produce new infectious particles.

Assembly

This is the assembly point where newly formed viral genetic material and proteins are combined to form complete viruses. All these components fit into place in the host cell cytoplasm in the form of fully functional virus particles. This is a very efficient process and readies the viruses for their next cycle of virus reproduction. From here onwards, those viruses leave the host cell to infect other cells and continue the infection cycle.

Release

The final step in the virus cycle of life is the release of the new virus particles. Lysis is when the host cell bursts open and releases a large number of viruses, but kills it in the process.

This is where the viruses break out of the host cell's membrane, taking along a portion of it to be their envelope, which excludes them from the reach of the immune system. This makes sure that the cycle of virus production continues because newly formed viruses move to other cells and repeat through the same cycle.

The Virus Life Cycle- Lysogenic Cycle

The following explains how viruses infect and replicate within the host's machinery and spread to other cells. Understanding the virus life cycle can help in knowing its course and designing antidotes against it.

Attachment

In a lysogenic cycle, the phage genome enters the cell through attachment and penetration. An example of a phage with this kind of life cycle is the lambda phage.

Entry

Instead of killing the host, the phage genome integrates into the bacterial chromosome and becomes a part of the genome of host. The integrated phage genome is called a prophage.

Replication

It is typical of the phages to be latent or inactive within the cell. As the bacterium replicates its chromosome, the phage’s DNA is also replicated and passed on to new daughter cells during reproduction.

Assembly and Release

During lysogeny, the prophage will be in the host chromosome until induction, which leads to the excision of the viral genome from the host chromosome.

After induction has occurred, the temperate phage can proceed through a lytic cycle and then undergo lysogeny in a newly infected cell.

Facts on Coronavirus

The following points explain how coronavirus infects human cells, multiplies, and spreads. This helps us understand how the virus causes illness and escapes the immune system.

• The virus then latches onto human cells by binding to a protein called ACE2, thus beginning the life cycle of the virus.

• It penetrates the human cells, hides from the immune system, and initiates virus replication.

• Inside the cell, it captures that the cell makes copies of its RNA and produces viral proteins for virus reproduction.

• The virus, with its replicated RNA and proteins, puts together new particles.

• It buds out of the cell, taking part of the membrane of the cell in a coat, in order not to be detected.

• The newly produced viruses spread to infect other cells, perpetuating the life cycle of the virus and ensuring more virus reproduction.

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