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8. Role in research

The main goal of biologists has been the molecular study of viruses and their interaction with the host cell. The study of bacteriophage replication in bacteria discovered the existence of messenger RNA, carrying the genetic code of DNA needed for protein synthesis. Studies with these viruses have also been instrumental in defining the biochemical factors that start and end the use of genetic information. Knowledge of the mechanisms of control of viral replication is critical to understanding the biochemical events in higher organisms.

The viruses are useful as model systems for studying the mechanisms that control genetic information, because in essence are small pieces of information. This allows scientists to study replication systems simpler and more manageable, but that function on the same principles as those of the host cell. Much of the research on the virus replicative pretends to know the mechanism to find and how to control growth and eliminate viral diseases. Studies on viral diseases have greatly contributed to understanding the body’s immune response against infectious agents. Studying this response have been thoroughly described serum antibodies and the secretions of mucous membranes, which help the body eliminate foreign elements such as viruses. Now, the scientific interest is focused on research designed to isolate certain viral genes. They could clone to produce large quantities of certain proteins, which would be used as vaccines.

9. Bacteriophage T4

This transmission electron micrograph shows a T4 bacteriophage, a virus that infects only bacteria (in some cases only Escherichia coli). Phages lack any reproductive mechanism and exploit the mechanisms of the bacterium to replicate. They do this by holding on to the cell walls with fibers, by way of legs, visible here. The tail is a sheath that contracts to inject the contents of the head, the genetic material (DNA) within the host. In 25 minutes, are capable of successfully using the reproductive mechanisms of bacteria and viral progeny fills the cell. Then, the packed bacteria burst, releasing about 100 new copies of the bacteriophage.

10. Viral Structure

Some bacteriophages (viruses that parasitize bacteria), left, have a rather complicated structure and sophisticated. The phage T4, pictured here, consists of five proteins and the following parts: head, tail, a collar or necklace, a basal plate and fibers for legs. In contrast, a flu virus, right, is simpler. A lipid envelope surrounding the protein shell, or capsid, which, like the bacteriophage genetic material coiled locks. Since this involved projecting two types of protein in the form of spikes, which determine the properties of the virus infectivity. The human hosts must produce new immune defenses whenever they mutate, hence annual vaccinations are done.

11. Viral replication

Outside a host cell, a virus is an inert particle. But once inside the cell, the virus reproduces so many times and thousands of individuals who leave the cell to find others that parasitize. Pathogenic viruses act by destroying or damaging cells when they leave those in which have been reproduced.

12. Virus

Viruses are obligate intracellular parasites, particles composed of genetic material (DNA or RNA, but not both) surrounded by a protective protein coat. Are inert outside the host, inside, they enter a dynamic phase in which replicate using the host cell enzymes, nucleic acids, its amino acids and its mechanisms of reproduction. They carry out what they can not perform alone. Viral replication leads often damage to the host: diseases such as herpes, rabies, influenza, some cancers, polio and yellow fever are viral in origin. Between 1000 to 1500 known viruses, there are about 250 to cause disease in humans (about 100 of which cause the common cold), and 100 infect different animals.

credit to: Martín Buczyner

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